Background

The anatomy of the scapholunate interosseous ligament (SLIL) has been described qualitatively in great detail, with recognition of the dorsal component's importance for carpal stability. The purpose of this study was to define the quantitative anatomy of the dorsal SLIL and to assess the use of high-frequency ultrasound to image the dorsal SLIL.

Methods

We used high-frequency ultrasound imaging to evaluate 40 wrists in 20 volunteers and recorded the radial-ulnar (length) and dorsal-volar (thickness) dimensions of the dorsal SLIL and the dimensions of the scapholunate interval. We assessed the use of high-frequency ultrasound by comparing the length and thickness of the dorsal SLIL on ultrasound evaluation and open dissection of 12 cadaveric wrists. Student's t test was used to assess the relationship between measurements obtained on cadaver ultrasound and open dissection.

Results

In the volunteer wrists, the mean dorsal SLIL length was 7.5 ± 1.4 mm and thickness was 1.8 ± 0.4 mm; the mean scapholunate interval was 5.0 mm dorsally and 2.5 mm centrally. In the cadaver wrists, there was no difference in dorsal SLIL length or thickness between ultrasound and open dissection.

Conclusions

The dorsal SLIL is approximately 7.5 mm long and 1.8 mm thick. These parameters may be useful in treatment of SLIL injuries to restore the native anatomy. High-frequency ultrasound is a useful imaging technique to assess the dorsal SLIL, although further study is needed to assess the use of high-frequency ultrasound in detection of SLIL pathology.

Posterior elbow capsulotomy plus triceps lengthening facilitates passive elbow flexion in children with arthrogryposis multiplex congenita, allowing independent function for activities of daily living, such as feeding and self-care of the face and hair. The posterior aspect of the distal end of the humerus and the olecranon are identified by palpation and exposed via a curvilinear incision over the posterior aspect of the elbow. Identifying the osseous landmarks can be challenging in some patients. The ulnar nerve is identified and protected. The triceps tendon is isolated, and z-lengthening is performed. Next, the posterior elbow capsule is incised proximal to the tip of the olecranon to expose the joint surface, and the arthrotomy is continued incrementally along the medial and lateral capsule until elbow flexion increases by ≥40°, or past 90° (maximum, 120°), with contact between the lengthened ends of the triceps tendon for repair. The triceps tendon is then repaired in the elongated position. After the wound is closed, the elbow is placed in flexion and immobilized in a cast. Alternative treatments include passive stretching exercises to increase elbow flexion. Elbow extension contractures result in substantial limitations in the activities of daily living for children with arthrogryposis multiplex congenita. Those who fail to attain at least 90° of elbow flexion with passive stretching in the first year of life benefit from posterior elbow release and triceps lengthening. In addition, children with <30° of passive elbow flexion are at risk of developing valgus instability of the elbow from passive flexion exercises because the axis of rotation of the elbow is difficult to detect. Once passive elbow flexion is attained, such children may be candidates for tendon transfers allowing active elbow flexion.

Objective

To evaluate the association of maternal delivery history with a brachial plexus birth injury risk in subsequent deliveries and to estimate the effect of subsequent delivery method on brachial plexus birth injury risk.

Methods

We conducted a retrospective cohort study of all live-birth deliveries occurring in California-licensed hospitals from 1996 to 2012. The primary outcome was recurrent brachial plexus birth injury in a subsequent pregnancy. The exposure was delivery history (parity, shoulder dystocia in a previous delivery, or previously delivering a neonate with brachial plexus birth injury). Multiple logistic regression was used to model adjusted associations of delivery history with brachial plexus birth injury in a subsequent pregnancy. The adjusted risk and adjusted risk difference for brachial plexus birth injury between vaginal and cesarean deliveries in subsequent pregnancies were determined, stratified by delivery history, and the number of cesarean deliveries needed to prevent one brachial plexus birth injury was determined.

Results

Of 6,286,324 neonates delivered by 4,104,825 individuals, 7,762 (0.12%) were diagnosed with a brachial plexus birth injury. Higher parity was associated with a 5.7% decrease in brachial plexus birth injury risk with each subsequent delivery (adjusted odds ratio [aOR] 0.94, 95% CI 0.92-0.97). Shoulder dystocia or brachial plexus birth injury in a previous delivery was associated with fivefold (0.58% vs 0.11%, aOR 5.39, 95% CI 4.10-7.08) and 17-fold (1.58% vs 0.11%, aOR 17.22, 95% CI 13.31-22.27) increases in brachial plexus birth injury risk, respectively. Among individuals with a history of delivering a neonate with a brachial plexus birth injury, cesarean delivery was associated with a 73.0% decrease in brachial plexus birth injury risk (0.60% vs 2.21%, aOR 0.27, 95% CI 0.13-0.55) compared with an 87.9% decrease in brachial plexus birth injury risk (0.02% vs 0.15%, aOR 0.12, 95% CI 0.10-0.15) in individuals without this history. Among individuals with a history of brachial plexus birth injury, 48.1 cesarean deliveries are needed to prevent one brachial plexus birth injury.

Conclusions

Parity, previous shoulder dystocia, and previously delivering a neonate with brachial plexus birth injury are associated with future brachial plexus birth injury risk. These factors are identifiable prenatally and can inform discussions with pregnant individuals regarding brachial plexus birth injury risk and planned mode of delivery.