Heesuk Kang, Paul Park, Frank La Marca, Scott J. Hollister and Chia-Ying Lin
The goal of this study was to evaluate and compare load sharing of the facet and uncovertebral joints after total cervical disc arthroplasty using 3 different implant designs.
Three-dimensional voxel finite element models were built for the C5–6 spine unit based on CT images acquired from a candidate patient for cervical disc arthroplasty. Models of facet and uncovertebral joints were added and artificial discs were placed in the intervertebral disc space. Finite element analyses were conducted under normal physiological loads for flexion, extension, and lateral bending to evaluate von Mises stresses and strain energy density (SED) levels at the joints.
The Bryan disc imposed the greatest average stress and SED levels at facet and uncovertebral joints with flexion-extension and lateral bending, while the ProDisc-C and Prestige LP discs transferred less load due to their rigid cores. However, all artificial discs showed increased loads at the joints in lateral bending, which may be attributed to direct impinging contact force.
In unconstrained/semiconstrained prostheses with different core rigidity, the shared loads at the joints differ, and greater flexibility may result in greater joint loads. With respect to the 3 artificial discs studied, load sharing of the Bryan disc was highest and was closest to normal load sharing with the facet and uncovertebral joints. The Prestige LP and ProDisc-C carried more load through their rigid core, resulting in decreased load transmission to the facet and uncovertebral joints.
Laura G. Hamant, P. David Adelson, Paul Kang, S. Danielle Brown and Jorge I. Arango
The goal of this study was to determine the functional efficacy of acellular processed nerve allograft (ALG) as compared to sural nerve autograft (AUG) harvested at time of surgery for children with obstetrical brachial plexus injury (OBPI).
A retrospective review of records was performed in patients who underwent surgical repair of OBPI between 2009 and 2015 at Phoenix Children’s Hospital. Patients were grouped based on the type of nerve graft used (AUG using the patient’s own sural nerve or decellularized processed cadaveric nerve ALG) and compared in terms of motor strength, British Medical Research Council score, functionality (Mallet scale score), surgical time, rate of complications, and need for further intervention.
A total of 52 records were identified meeting study criteria. Sural nerve AUG was used in 22 cases and ALG in 30 cases. Changes from pre- to postsurgical assessment of motor strength were significant for all muscle groups measured except for elbow extension for both groups. All Mallet scores increased significantly. No significant differences were observed in motor strength and functional components between groups. Interventions using ALG had shorter operative times than those performed using AUG. No significant difference was observed in terms of need for further intervention. Two patients (9%) in the AUG group developed stitch abscesses at the harvest site, whereas there were no infectious complications reported in the ALG group.
These findings suggest equivalence in terms of muscle strength and functional outcomes between the use of AUG and ALG for patients with OBPI. However, the less invasive character of ALG repair decreases surgical time and risk of complications.