Facial Nerve Dysfunction After Mandibular Distraction Osteogenesis in Patients with Robin Sequence: A Systematic Review and Meta-Analysis

Objective Robin Sequence (RS), characterized by micrognathia, glossoptosis, and upper airway obstruction, is an increasingly recognized diagnosis. An effective surgical intervention is mandibular distraction osteogenesis (MDO). This study analyzes published evidence regarding facial nerve dysfunction (FND) associated with MDO. Design and Setting According to PRISMA guidelines, a systematic review was carried out with databases queried in June 2019 using MESH terms, or equivalent terms, as follows: “distraction osteogenesis” and “Robin Sequence”. A review of original Spanish and English articles, were included. Outcome measures included the prevalence of FND; the affected branches; the rate of permanent vs. transient FND; the use of an internal vs. external device; the daily distraction rate; and finally, the overall distraction length. Subsequently, a meta-analysis was conducted to collate results regarding the prevalence of FND and the factors associated with it. Results Of 239 unique studies identified, 19 studies with 729 patients met inclusion criteria; 52 patients developed FND after MDO. A random-effects meta-analysis yielded a pooled prevalence of FND of 6.40%, with moderately heterogeneous studies (I2 = 41%, τ2 = 0.006). Marginal mandibular nerve involvement was most commonly noted. Nine studies reported transient FND, six permanent, one both, and two unspecified. Internal distractors were used in 8 studies and external in 3 and both in 2. Distraction rate was 1.00 to 2.00 mm/day and total distraction length ranged from 13.00 to 22.3 mm. Sample size was the only parameter inversely associated with rate of FND (p = 0.04). Conclusion This analysis of FND associated with MDO for patients with RS demonstrates a lack of consistent documentation. MDO-associated FND does not appear to be uncommon, and permanent dysfunction can occur. This review underscores the importance of thorough documentation to elucidate the mechanism of FND.

STRYDE versus PRECICE magnetic internal lengthening nail for femur lengthening

Introduction Magnetic internal lengthening nails (MILNs) have been used for femoral lengthening to avoid complications associated with external fixation. The titanium version of the MILN (PRECICE®) has been in use since 2011 but had limitations (50–75 lb) in post-operative weight bearing. A new stainless-steel version of the MILN (STRYDE®) allows 150–250 lb of post-operative weight bearing. The aim is to compare the outcomes of using these two different MILNs for both unilateral and bilateral femoral lengthening. Methods A single-center, retrospective cohort study was conducted in which patients’ records were reviewed from the period from January 2017 to March 2020. A total of 66 femoral lengthening procedures were included in the study and were divided into two groups: STRYDE® group (30 femora) and PRECICE® group (36 femora). Outcomes assessed were the 6-months post-operative Limb Deformity-Scoliosis Research Society (LD-SRS) Score, adjacent joint range of motion (ROM), average distraction rate, bone healing index (BHI), and complications. Results No statistically significant difference was found between the two groups in regard to the (LD-SRS) score, hip ROM, or knee ROM. Statistically significant differences were found between the two groups in regard to BHI (average of 0.84 months/cm and 0.67 months/cm for STRYDE® and PRECICE®, respectively) and distraction rate (average of 0.6 mm/day and 0.9 mm/day for STRYDE® and PRECICE®, respectively). No mechanical nail complications were reported in the STRYDE® group compared to three events of nail failure in the PRECICE® group. One femur in the PRECICE® group needed BMAC injection for delayed healing compared to four femurs in the STRYDE® group. Conclusion The STRYDE® MILN yields comparable functional results to those of PRECICE® MILN and shows fewer mechanical nail complications. However, STRYDE® MILN requires a slower distraction rate and yields slower healing (larger BHI). Level of evidence Level III, Therapeutic study.

Humerus Lengthening: A Comparison of the Internal Lengthening Nail to External Fixation

Introduction: Magnetic internal lengthening nails (MILNs) have been used for humeral lengthening to avoid complications associated with external fixation. Purpose/Questions: We compared the 1-year Disabilities of the Arm, Shoulder and Hand (DASH) score, adjacent joint range of motion (ROM), bone healing index (BHI), length achieved, distraction rate, and complications when lengthening the humerus using MILN vs using external fixation. Methods: We conducted a retrospective cohort study of 18 patients (22 humeri) from January 2001 to March 2020 divided into 2 groups, the MILN group (7 patients, 7 humeri) and the mono-lateral fixator group (11 patients, 15 humeri). Results: The MILN group showed larger improvement of DASH scores (average 26.8 and 8 for MILN and fixator groups, respectively), less loss of elbow ROM (average 5° and 7° for MILN and fixator groups, respectively), and shorter time to full recovery of elbow ROM (average 39 days and 122 days for MILN and fixator groups, respectively). In the MILN group, there was slower distraction rate (average 0.66 mm/day and 0.86 mm/day for MILN and fixator groups, respectively), less lengthening achieved (average 5.2 cm and 7 cm for MILN and fixator group, respectively), and a lower lengthening percentage (average 19% and 41% for MILN and fixator group, respectively). Bone healing index (BHI) of 0.94 and 0.99 months/cm for the MILN and the fixator groups were similar. Conclusion: Humeral lengthening using the MILN allowed for early full recovery of joint ROM with comparable functional and radiographic outcomes compared with using external fixators.

Development of a Force-Driven Distractor for Distraction Osteogenesis

Distraction osteogenesis is a routine surgical procedure to lengthen a long bone. A fixed lengthening rate is typically used. We investigate measuring forces continuously and producing a variable distraction rate. A motorized distractor was instrumented with a load cell to measure the forces developed in a limb during distraction osteogenesis. The motor moves 2.6 μm at each step, with a variable frequency depending on the distraction rate. The forces were measured every 15 s and used to change the rate on the autodistractor. The autodistractor, load cell, data logger, controller, and battery pack were all mounted on a monolateral rail fixator, which was tested on a sheep that underwent tibial lengthening. Results show the feasibility of continually recording forces in vivo. The lengthening rate changed automatically, based around a threshold force of 300 N. Findings indicate that force readings are feasible and practical with a simple device. Force determination may provide an additional means to evaluate tissue integrity in real-time and away from the clinic. An automatic variable rate device could improve limb lengthening.

Effect of Bilateral Mandibular Osteodistration on the Condylar Cartilage: An Experimental Study on Rabbits

Although various aspects of bone formation during distraction osteogenesis have been studied extensively, there are only limited experimental data concerning the influence of hyper-physiologic mandibular distraction rate on structural alterations in the temporomandibular joint (TMJ) condylar cartilage. The purpose of this study was to evaluate the effect of bilateral distraction osteogenesis of the mandibular body, at a hyper-physiologic rate and length, on the integrity of the condylar cartilage in rabbits. MATERIALS AND METHODS: Eighteen healthy adult male rabbits weighing 2 to 3 kg were assigned to 1 of 2 groups: the control group (n = 2 rabbits, 4 joints) or the study group (n = 16 rabbits, 32 joints) four rabbits (8 joints) in each subgroup according to the post-distraction period (1,2,3 or 4 weeks). In the control group, rabbits received sham surgery (Osteotomy without distraction) and then left to live for 4 weeks under the same condition of the study group then euthanized using intravenous overdose of pentobarbital sodium. In the study group, an extra oral custom-made distracter was employed to achieve bilateral mandibular hyper physiologic distraction (1.5 mm twice daily for 5 days) distraction. All animals were evaluated clinically and histomorphometrically and results analyzed by MINITABE 13.1 statistical package using ANOVA test. RESULTS: Animals underwent distraction showed obvious changes in condylar surface contour related to length of the follow up period, compared to the control; these changes seemed to be partly reversible. The most pronounced observation was the irregularities and resorption in the anterior part of the condylar cartilage and the subcondylar bone. Moreover, at the first two weeks, the area of resorption was invaded by large number of osteoclasts and chronic inflammatory cells which declined later in the 3rd and 4th weeks and replaced with osteoblastic activities. CONSLUSION: These experimental data showed that distraction rate of 3 mm per day may lead to degenerative or even early arthritic changes in the TMJ condylar cartilage in the 1st and 2nd post-distraction weeks. However, all condyles showed adaptive and remodeling sings in the following 3rd and 4th weeks.