Polylactic acid bioabsorbable implants of the hand: A review.

In the treatment of hand fractures, metal implants are often used to allow early range of motion and a stable fixation. Although they provide adequate bone union, metal implants have been known to cause joint stiffness, painful or prominent hardware, and adhesions, often leading to another surgery for hardware removal. Bioabsorbable implants have been shown to offer comparable results for fracture fixation in the hand while removing the complications seen with retained hardware. In this article, we review biomechanical and clinical studies focused on bioabsorbable implants made of polylactic acid used for orthopedic hand injuries in order to promote their continued use and future research.

Effects of A2 Pulley Venting on Bowstringing and Tendon Slack: A Biomechanical Investigation.

BACKGROUND: A2 pulley release is often needed for exposure of the lacerated tendon, retrieval of retracted tendons, placement of core sutures, or to permit full motion and gliding of the repaired and edematous tendon. However, there is no agreement in the literature on the specific quantity of pulley venting that can be performed and recommendations are limited to an undefined "judicious release" of the pulleys when necessary. METHODS: Following a previously developed testing protocols, finger kinematics, tendon excursion, and bowstringing were evaluated on cadaveric hands for venting in increments of 20% of the pulley length. RESULTS: In our study, we found a statistically significant influence of venting on bowstringing, although no difference was found between fingers, and a significant difference in tendon slack, which was variable depending on the finger. Bowstringing started increasing at 20% of A2 venting and peaked at full release. Tendon slack did not start until 40% of A2 venting on the index finger, but started at 20% on the middle, ring, and small fingers. CONCLUSIONS: Venting of the A2 pulley leads to an incremental increase in tendon bowstringing and tendon slack. However, differences in metacarpophalangeal flexion angle were not observed until full A2 pulley release, and only observed in the index finger, and no differences were observed in proximal interphalangeal flexion angles. Therefore, the benefit of releasing the A2 pulley when clinically necessary will likely outweigh the risks of loss of motion or strength.

Nitinol Memory Rods Versus Titanium Rods: A Biomechanical Comparison of Posterior Spinal Instrumentation in a Synthetic Corpectomy Model.

STUDY DESIGN: Biomechanical investigation. OBJECTIVE: To compare the biomechanical performance of nitinol memory metal rods and titanium rods when used as posterior spinal instrumentation in a synthetic model. METHODS: Biomechanical testing was performed using ultra-high-molecular-weight polyethylene blocks. Nineteen spinal constructs were created to allow comparison of 5.5-mm nitinol rods with 5.5-mm titanium rods. Static compression and rotational testing were performed on an Instron 8874 and Instron 4202 at 37°C to simulate body temperature. RESULTS: The average titanium construct stiffness under static compression or bending was 47.2 ± 9.1 N/mm while nitinol's stiffness averaged 48.9 ± 12.4 N/mm (P = .83). During axial rotation testing, the nitinol rod system showed no torsional stiffness difference from the titanium system: 0.95 ± 0.03 Nm/deg versus 0.96 ± 0.17 Nm/deg, respectively (P = 0.91). There was a statistically significant difference between the average torsional yield point for the titanium constructs (14.4 ± 1.6 Nm/deg) and nitinol constructs (21.3 ± 0.8 Nm/deg) (P = .004). The torsional toughness of the nitinol constructs was also statistically greater than the titanium rods: 473 GN/m3 versus 784 GN/m3 (P = .0006). There was no statistically significant difference between the nitinol group sustaining a higher number of fatigue cycles until failure and the titanium group (181 660 cycles vs 64 104 cycles, respectively, P = .22). CONCLUSIONS: This study provides biomechanical evidence that nitinol rods used in a posterior construct are comparable to titanium rods with regard to compression and have increased torsional failure load and torsional toughness. While nitinol trended toward superior fatigue resistance, there was no significant difference in nitinol versus titanium construct fatigue resistance.

Experimental Evaluation of the Elson Test Efficiency Following Central Slip Injury.

Purpose: The purpose of this article is to explore the amount of work, quantitated by flexion and extension cycles, that is needed to obtain a positive Elson test following a central slip injury. Methods: Thirteen frozen cadaveric fingers from individuals with an average age of 79.6 years were used. Testing was performed by imposing sinusoidal displacement of the 2 tendons, with loads ranging from 30 N to 2 N at 1 Hz. Following transection to the central slip, each finger was cycled 1,000 times using the same protocol adopted for the control. Following 100, 200, 300, and 1,000 cycles, we measured the extension angles of the metacarpophalangeal, proximal interphalangeal, and distal interphalangeal joints from the flexed position and the distance between landmarks of the extensor apparatus and simulated an Elson test. Results: In both the fingers, the range of motion of the metacarpophalangeal and distal interphalangeal joints measured in the controls remained unchanged, whereas the range of motion of the proximal interphalangeal joint was significantly reduced immediately after central slip transection. Combining both ring and middle fingers, for a displacement of 5 mm, the force measured in the control (1.05 ± 0.69 N) increased to the value of 2.36 ± 0.97 N at the 1,000th cycle. Although the middle finger has shown a significant difference in force at 100 cycles following central slip transection, 200 cycles were needed to observe a difference on the ring finger. Conclusions: In controlled conditions, there is a variation in resistance to flexion of the distal interphalangeal joint. However, the amplitude of the forces is so small that they are likely imperceptible clinically. Delayed testing should be considered to increase the sensitivity of the test or in patients experiencing pain. Type of study/level of evidence: Diagnostic V.

Design and implementation of a system-based course in musculoskeletal medicine for medical students.

BACKGROUND: The amount of time devoted to musculoskeletal medicine in the typical undergraduate curriculum is disproportionately low compared with the frequency of musculoskeletal complaints that occur in a general practice. Consequently, whether because of the quantity or quality of the education, the competence level of graduating physicians regarding musculoskeletal problems is inadequate. Our purposes were to design a self-contained, system-based course in musculoskeletal medicine for medical students in the preclinical years and to measure the level of competence achieved by a class of first-year medical students who took the course. METHODS: The course was formulated by faculty from the departments of orthopaedic surgery, anatomy, and rheumatology and included elements of both objectives-based and problem-centered curricular models. The clinical lectures were preceded by pertinent anatomy lectures and dissections to provide a context for the clinical information. The lectures on basic science were designed to rationalize and explicate clinical practices. Small-group activities were incorporated to permit engagement of the students in critical thinking and problem-solving. A general musculoskeletal physical examination was taught in two two-hour-long small-group sessions with the orthopaedic residents serving as instructors. Cognitive competency was evaluated with use of comprehensive anatomy laboratory and written examinations, the latter of which included a validated basic competency examination in musculoskeletal medicine. Process-based skills were evaluated in the small-group meetings and in a timed, mock patient encounter in which each student's ability to perform the general musculoskeletal physical examination was assessed. RESULTS: The course lasted six weeks and consisted of forty-four lecture hours, seventeen hours of small-group meetings, and twenty-eight hours of anatomy laboratory. The average student score on the basic competency examination was 77.8%, compared with 59.6% for a historical comparison group (p < 0.05). Each student demonstrated the ability to adequately perform a general musculoskeletal physical examination in twenty minutes. The survey of student opinion after the course indicated a high level of student satisfaction. CONCLUSIONS: The main features of the course were: (1) an emphasis on both cognitive and process-based knowledge; (2) more contact hours and broader content than in previously described courses in musculoskeletal medicine; (3) the use of small groups to focus on problem-solving and physical examination competencies; (4) basic-science content directly related to clinical goals. These features might be used at other institutions that employ a system-based curriculum for the preclinical years to help improve competence in musculoskeletal medicine.

The septa of Legueu and Juvara: an anatomic study.

PURPOSE: To study the anatomy of the septa of Legueu and Juvara and interpalmar plate ligaments (IPPLs) of the hand. MATERIALS: Eleven cadaver hands were dissected. The number, attachments, dimensions, and relationships of the septa and IPPLs to other structures were determined. RESULTS: Eight septa were identified radial and ulnar for each digit. The radial were longer than the ulnar septa. The septa attached to the transverse ligament of the palmar aponeurosis superficially and to the soft-tissue confluence deeper and distally. They formed 7 compartments of 2 types flexor septal canals that contained the flexor tendons and web space canals that contained common digital nerves and arteries and lumbrical muscles. Grossly and histologically the septa were thicker and consisted of organized collagen distally but not proximally. Three IPPLs were identified: radial, central, and ulnar. These formed the floors of the second, third, and fourth web space canals. The IPPLs were more substantial, thicker, and had more fibrous appearance from radial to ulnar. The fibers of the radial and central IPPLs were oriented transversely, whereas those of the ulnar IPPL were oriented obliquely. CONCLUSIONS: Awareness of the anatomy of deep retinacular structures of the hand is important for surgical exposure in this area and possible involvement in conditions such as Dupuytren's disease.

Dupuytren's cord involving the septa of Legueu and Juvara: a case report.

A patient with Dupuytren's disease with involvement of the palmar fascial complex and digital contracture is described. A vertical cord had developed in the transverse ligament of the palmar aponeurosis fibers and the underlying septa of Legueu and Juvara. The cord was composed of a pretendinous band, transverse ligament of the palmar aponeurosis, and septum of Legueu and Juvara. The cord was attached deeply in the soft tissue confluence of the sagittal band, palmar plate, and interpalmar plate ligament. Involvement of the transverse ligament of the palmar aponeurosis and septa of Legueu and Juvara in Dupuytren's disease is rare. Understanding of the normal and pathologic fascial anatomy explains their simultaneous involvement and is necessary for complete ablation of the diseased tissue.