Force measurements during posterior calvarial vault osteodistraction: A novel measurement method

Posterior cranial vault distraction in children with syndromic craniosynostosis: the era of biodegradable materials-a comprehensive review of the literature and proposed novel global application

Distraction osteogenesis is utilized to increase intracranial volume in the treatment of restrictive pathologies, most commonly syndromic synostosis. Children too young for open calvarial vault expansion or other systemic or local contraindications to a direct reconstructive approach benefit greatly from distraction osteogenesis, typically addressing posterior vault expansion. Wound infection, cerebrospinal fluid (CSF) leak, device failure, need for a second surgery for removal, and cost, are issues that can limit the use of this approach. These challenges are more pronounced in low- and middle-income countries (LMICs) due to lack of access to the device, the financial burden of the need for a second surgery, and the severity of the implications of infection and CSF leak. Over the last five decades, there has been an increased acceptance of bioresorbable instrumentation in craniofacial surgery. Poly L-lactic acid, polyglycolic acid, and polydioxanone are the most commonly used polymers. New resorbable fixation tools such as ultrasound-activated pins and heat-activated pins are superior to conventional bioresorbable screws in allowing attachment to thinner bone plates. In this paper, we present a review of the literature on cranial vault distraction and the use of bioresorbable materials and propose a novel design of a fully absorbable cranial distractor system using external magnetic distraction control, eliminating the need for external activation ports and a second surgery to remove the hardware. The application of this technology in LMIC settings could advance access to care and treatment options for patients with syndromic synostosis.

Treatment of Syndromic Craniosynostosis by Anterior and Posterior Vault Distraction Osteogenesis (A-PVDO)

OBJECTIVE

To explore the feasibility and therapeutic effect of anterior and posterior vault distraction osteogenesis (A-PVDO) in the treatment of infantile syndromic craniosynostosis.

METHODS

Between January 2017 and December 2019, 7 children with syndromic craniosynostosis underwent osteotomy with Piezo-surgery at our hospital. The first step was to harvest the frontal bone flap and the orbitofrontal bone flap. The second step was to separate the scalp and expose the posterior occipital. Osteotomy was performed on the occipital tubercle. Thereafter, 2 distractors were horizontally installed on the upper edge of the anterior cranial orbit, 2 distractors of 3 cm were installed on the posterior cranial bone. Meanwhile, lambdoidal sutures were fixed by titanium plates. Bone distraction was initiated on postoperative day 5 at the rate of 0.4 to 0.6 mm/day, twice per-day, for a total of 10 to 15 days. After 6 months, the distractors and the titanium plates were removed by secondary surgery.

RESULTS

The intracranial volume and posterior cranial morphology were recorded during the follow-up of 6 to 14 months (average = 12 months). The posterior craniums of 7 cases with lambdoidal sutures fixation were completely extended. The anterior cranial morphology was normal. All the cranial deformities were significantly improved. There were no severe complications, such as death, cranial necrosis, and intracranial infection.

CONCLUSIONS

A-PVDO is an ideal method for the treatment of severe syndromic craniosynostosis, which can achieve more natural appearance than anterior vault distraction osteogenesis or posterior vault distraction osteogenesis. Moreover, A-PVDO causes no severe complications and is suitable for the treatment of severe syndromic craniosynostosis.

Forces Exerted in Craniofacial Distraction Osteogenesis

BACKGROUND

The purpose of this study was to develop a methodology for quantifying linear forces of distraction osteogenesis, and thereafter apply this methodology to measure and compare distraction force magnitudes between cranial vault distraction osteogenesis (CVDO) and mandibular distraction osteogenesis (MDO).

METHODS

Patients undergoing CVDO or MDO as inpatients had distraction forces acquired with a digital torque-measuring screwdriver. Torque measurements were then converted into linear distraction force values, which were then compared across distraction types and protocols with appropriate statistics.

RESULTS

CVDO was performed on 7 patients (41.2%), and MDO was performed on 10 patients (58.8%). Across the entire cohort, the average maximum force per activation was 27.0 N, and the average elastic force was 10.7 N. Maximum force (CVDO: 52.9 N versus MDO: 12.9 N; P < 0.001) and elastic force (CVDO: 22.0 N versus MDO: 4.5 N; P < 0.001) were significantly higher in patients undergoing CVDO than MDO. Multivariate regression demonstrated that maximum activation force was significantly associated with sequential days of distraction (B= + 1.1 N/day; P < 0.001), distraction rate (B= + 8.9 N/mm/day; P = 0.016), distractor hardware failure (B= + 10.3 N if failure; P = 0.004), and distraction type (B= + 41.4 N if CVDO; P < 0.001).

CONCLUSIONS

Cranial vault distraction requires significantly more linear distraction force than mandibular distraction. Maximum forces increase with each day of distraction, as well as with increased distraction rates. Linear distraction force methodology from this study may provide the foundation for future development of optimized procedure-specific or patient-specific distraction protocols.

A Review on Variability in Treatment Protocols With Posterior Cranial Vault Distraction

BACKGROUND

Prior studies have confirmed the ability of posterior cranial vault distraction osteogenesis (PVDO) to expand the intracranial volume in patients with craniosynostosis. To date, there is scant literature on the optimal distraction protocol for PVDO. The authors sought to review the literature and define a common protocol for posterior cranial vault distraction.

METHODS

The authors performed a systematic review for published PVDO protocols. The data collected from these studies included age at the time of PVDO, number of distraction devices placed, time for latency, rate and rhythm of distraction, distraction length, time for consolidation, and surgical outcomes.

RESULTS

A total of 286 patients were identified within 24 studies from 2011 to 2019. The mean age of patients identified was 25.34 months. After application of distractors, latency period ranged between 1 and 7 days, with most patients undergoing 5 to 7 days of latency. Once distraction was begun, the majority of patients (77.4%) underwent 1 mm of distraction daily. Total lengths of distraction ranged between 13 and 35 mm, with the largest cohort of patients undergoing 26 to 30 mm of total distraction. A total of 60 complications were reported for a total of 212 patients, yielding an overall complication rate of 28.3%.

CONCLUSIONS

Although there is variability in reported PVDO protocols, the majority are similar to distraction osteogenesis protocols described for long bone sites. Increased patient age correlates with selection of a greater latency period and total distraction length, while frequency of complications is also increased.