Venous thromboembolism prophylaxis after total joint arthroplasty

Venous thromboembolism (VTE) prophylaxis after total joint arthroplasty is considered best practice. However, over the past 5 years, there has been considerable debate about the ideal prophylactic regimen or modality. The American Academy of Orthopaedic Surgeons and the American College of Chest Physicians published their most recent clinical practice guidelines about VTE prophylaxis in 2011 and 2012, respectively. In addition, the Surgical Care Improvement Project published their latest recommendations in 2014. In this review, commonly used VTE prophylaxis options and the latest clinical guidelines will be discussed.

Patient care, professionalism, and relations with industry

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Management of irreparable rotator cuff tears and glenohumeral arthritis

Glenohumeral arthritis with irreparable rotator cuff tears remain a difficult entity to treat. Varied causes include rotator cuff tear arthropathy, osteoarthritis, or rheumatoid arthritis with irreparable cuff tear. Common symptoms are progressive pain and dysfunction. Physical examination may reveal pain, crepitance, rotator cuff weakness, and loss of motion and function. Radiographs may reveal varying degrees of osteophyte formation, sclerotic bone, superior humeral head migration, and bony erosion. Additional imaging modalities may reveal cuff tear size, retraction, atrophy, and fatty infiltration. Failure of nonoperative management may lead to operative intervention. Rotator cuff repair or reconstruction may help prevent progression of tears and future arthritic changes. In patients with moderate to severe glenohumeral arthritis and irreparable rotator cuff tears, hemiarthroplasty is currently the procedure of choice. For patients with severe cuff dysfunction or loss of coracoacromial arch, or for patients who require revision, the reverse shoulder prosthesis may offer a treatment option. Future management continues to be defined with additional study.

Characterization of load-length-velocity relationships of nine different skeletal muscles

A three-dimensional characterization of muscle load, length and velocity was obtained from nine muscles in the cat's hind limb through contractions where the muscles shortened against inertial-gravitational loads. A model based on the load-length characteristic and second-order dynamics describes shortening velocity related to load and length under these conditions. We conclude that this model describes well contraction velocity as function of length and load under inertial-gravitational load conditions, with correlation coefficients higher than 0.9 in most of the tested muscles.

Mechanoreceptors in the human elbow ligaments

The medial, annular, and lateral elbow ligaments from 6 fresh human cadavers were dissected from origin to insertion, stained, and examined with a light microscope to determine the existence of mechanoreceptors. It was shown that the anterior, posterior, and transverse medial ligaments as well as the annular and radial collateral ligaments were endowed with mechanoreceptors. The mechanoreceptors consisted of Golgi organs, Ruffini terminals, Pacinian corpuscles, and free nerve endings. The mechanoreceptors were distributed evenly throughout the annular and transverse medial ligament, but with increased density toward the origin and distal insertions in the radial, posterior, and anterior medial ligaments. It was concluded that the elbow ligaments may provide significant sensory function to the elbow joint, in addition to being its major mechanical restraints.

Ligamentomuscular protective reflex in the elbow

A reflex are from the medial elbow ligaments to the forearm pronator muscles was shown to exist in the feline model. A single articular branch emerging from the median nerve and converging on the medial collateral ligament was identified and stimulated with supramaximal pulses of 100 microseconds duration at a rate of 10 pulses/s. Stimulation of the articular nerve elicited myoelectric activity in the flexor digitorum superficialis, flexor digitorum profundus, flexor carpi radialis, flexor carpi ulnaris, and pronator teres. Transection of the articular nerve between the electrodes and the median nerve resulted in the disappearance of any myoelectric activity in the muscles, thus confirming the afferent nature of the articular nerve. The mean time delay from the application of the stimulus to the corresponding myoelectric discharge ranged from 3.2 to 5.8 ms for the 5 muscles. The existence of a fast-acting reflex arc from the medial elbow ligaments to the forearm muscles both confirms the concept of ligamentomuscular protective synergy (shown to exist in the knee, shoulder, and ankle joints) and extends it to the elbow. This reflex arc has significant implications for both the planning of elbow surgery while preserving the neural supply of the ligaments and for the planning of postsurgical or conservative therapeutic rehabilitation modalities.

Reciprocating gait orthosis powered with electrical muscle stimulation (RGO II). Part II: Medical evaluation of 70 paraplegic patients

Medical evaluation was performed on a group of paraplegics who were trained to walk with the Reciprocating Gait Orthosis powered with electrical muscle stimulation (RGO II). The evaluation included changes in spasticity, cholesterol level, bone metabolism, cardiac output and stroke volume, vital capacity, knee extensors torque, and heart rate at the end of a 30-meter walk. After an average of 14 weeks of training during which patients walked for 3 hours per week, significant reductions in spasticity, total cholesterol and low-density lipids, hydroxyproline/creatinine ratio, and increased knee extensor torque were evident. The data also showed that improvements occurred in the calcium/creatinine ratio, serum calcium and alkaline phosphatase levels, cardiac output and stroke volume, and vital capacity, yet these improvements were not statistically significant. The final heart rate at the end of a 30-meter walk showed that the RGO II required only a moderate level of exertion, which was found to be the lowest among the other mechanical or muscle stimulation orthoses available to paraplegics. It was concluded that the limited but reasonable level of functional regain provided by the RGO II is associated with a general improvement in the paraplegic's physiological condition if used for a minimum of 3 to 4 hours per week.

Accuracy of formula-derived creatinine clearance in paraplegic subjects

The usefulness of formula-derived creatinine clearance (CC) is not well established among the paraplegic population. We prospectively collected 24-hour-urines from paraplegic subjects, obtaining 81 collections from 42 patients over 27 months. After validation, 57 collections were used to obtain measured CC. CCs were also estimated using several formulae. Measured CC and estimated CC were then compared. In the case of the Cockroft-Gault formula, the overall correlation was excellent, with an r value of 0.88 and p = 0.0001. In our study 40, 70, and 93% of the estimated CCs were within 10, 20, and 33% of the measured CCs. These numbers are similar to the ones reported by Cockroft and Gault. Also, the data on measured creatinine clearance in paraplegics compared favorably with parallel data obtained from nonparaplegics (91 24-hour-urine collections, 65 validated). We conclude that the Cockroft-Gault formula (and other formulae) estimate creatinine clearance as accurately in the paraplegic population as they do in the nonparaplegic population.

Reciprocating gait orthosis powered with electrical muscle stimulation (RGO II). Part I: Performance evaluation of 70 paraplegic patients

Seventy paraplegics were fitted with an improved Reciprocating Gait Orthosis powered with or without (low-level injury) electrical stimulation of the thigh muscles (RGO II) as a secondary rehabilitation phase after the acute period. The patients comprised a broad cross-section of the paraplegic population applying for medical services and varied in age from 16 to 55 years, time since injury ranging from less than 1 to 15 years, injury levels ranging from C-6/7 to T-11/12, and varying levels of spasticity, contractures, scoliosis and other related medical and physiologic problems. The success/failure ratio was dependent on the injury level, which was 1:1 for paraplegics with injury level at C-6/7; 1.67:1 for those with injury of T-1/3; and about 4:1 for paraplegics with injury level from T-3 to T-12. Lack of motivation and medical problems unrelated to the RGO II treatment were the primary reasons for failure. The duration of treatment (outpatient service three times per week) ranged from 2 to 48 weeks (mean: 16). Forty-one patients who completed the RGO II rehabilitation and were sent home with the orthosis for independent use (for at least 6 months and up to 3 years) were surveyed by a staff member for analysis of the meaning and impact of the RGO II on the patient's life and health, and potential problems. It was shown that 80.5% of the 41 patients were regular users and 19.5% were non-users. Thirty-eight of the 41 patients declined an offer to return the RGO II equipment for a full refund, while three patients were willing to return the orthosis. It was concluded that the RGO II is viable orthosis for restoring standing and limited walking in paraplegics while providing sufficient function, safety, and reliability. The most appropriate patients for the use of such an orthosis consist primarily of those with T-3 to T-12 injury level and good motivation, although highly selected patients with higher injury levels also can benefit from its use. Regular use of the RGO II, even for exercise only, had a general positive impact on the patients' health and outlook.