Spring-assisted surgery-a surgeon's manual for the manufacture and utilization of springs in craniofacial surgery.

BACKGROUND AND PURPOSE: Spring-assisted surgery has been used for the treatment of craniofacial deformities since its 1997 inception in Sweden by Dr Lauritzen (Scand J Plast Reconstr Surg Hand Surg 1998;32:331-338). Initial applications have focused on the treatment of patients with single-suture craniosynostosis. Recently, indications and applications have expanded to include patients with syndromic craniosynostosis, multiple-suture synostosis, and midface hypoplasia. The advancement of spring-assisted surgery in this country has been hindered by the need for patient-specific spring fabrication because few surgeons understand how to make the springs for each application. We will review our spring design and treatment algorithms to facilitate wider use of this innovative treatment modality. METHODS: This is a retrospective institutional review board-approved analysis of the spring design for our first 90 cases of spring-assisted surgery used to treat sagittal synostosis at the North Carolina Center for Cleft and Craniofacial Deformities. Outcome analysis was done to generate a treatment algorithm based on diagnosis, patient age, spring design, number of springs, spring force and expansion, and clinical outcome. RESULTS: Ninety children with sagittal craniosynostosis (64 males, 26 females) were treated during an 8-year period (2001-2009) with spring-assisted surgery. Mean age at treatment was 4.4 months and mean age at spring removal was 8.8 months. Mean number of springs used was 2 (range, 1-3). Mean spring force used in sagittal synostosis was 5.5-9.5 (range) for the anterior spring and 5.5-9.5 (range) for the posterior spring with a mean posttreatment expansion of 6.65 cm. Analysis of the results shows that spring force and expansion required for optimal correction is dependent on the age at surgery, type of the deformity, and severity of the deformity. Specifically, the younger the child, the weaker the spring needed for surgical correction. General principles for spring application for scaphocephaly include (1) the longer the anterior posterior dimension of the skull deformity, the more likely a third spring is necessary; (2) the narrower the posterior occiput, the stronger the posterior spring required; and (3) if a postcoronal band is seen in the calvarium, a stronger anterior spring is needed. CONCLUSIONS: Long-term experience with spring-assisted surgery has facilitated the development of standardized, reproducible techniques allowing spring design modifications to optimize clinical outcome.

Ameliorating Spinal Cord Injury in an Animal Model With Mechanical Tissue Resuscitation.

BACKGROUND: Traumatic spinal cord injury (SCI) is a major worldwide cause of mortality and disability with limited treatment options. Previous research applying controlled negative pressure to traumatic brain injury in rat and swine models resulted in smaller injuries and more rapid recovery. OBJECTIVE: To examine the effects of the application of a controlled vacuum (mechanical tissue resuscitation [MTR]) to SCI in a rat model under several magnitudes of vacuum. METHODS: Controlled contusion SCIs were created in rats. Vacuums of -50 and -75 mm Hg were compared. Analysis included open-field locomotor performance, magnetic resonance imaging (in vivo T2, ex vivo diffusion tensor imaging and fiber tractography), and histological assessments. RESULTS: MTR treatment significantly improved the locomotor recovery from a Basso, Beattie, and Bresnahan score of 7.8 ± 1.9 to 11.4 ± 1.2 and 10.7 ± 1.9 at -50- and -75-mm Hg pressures, respectively, 4 weeks after injury. Both pressures also reduced fluid accumulations > 10% by T2-imaging in SCI sites. The mean fiber number and mean fiber length were greater across injured sites after MTR treatment, especially with treatment with -50 mm Hg. Myelin volume was increased significantly by 60% in the group treated with -50 mm Hg. CONCLUSION: MTR of SCI in a rat model is effective in reducing edema in the injured cord, preserving myelin survival, and improving the rate and quantity of functional recovery. ABBREVIATIONS: BBB, Basso, Beattie, and BresnahanDTI, diffusion tensor imagingFA, fractional anisotropyMTR, mechanical tissue resuscitationMTR50, mechanical tissue resuscitation with 50-mm Hg subatmospheric pressureMTR75, mechanical tissue resuscitation with 75-mm Hg subatmospheric pressureROI, region of interestSCI, spinal cord injury.

Dislocation of rotating hinge total knee prostheses. A biomechanical analysis.

BACKGROUND: Symptomatic instability and implant dislocation are occasionally encountered in patients with a rotating hinge total knee prosthesis. A biomechanical study of rotating hinge total knee implants was performed to determine the association between the design (length and taper) of the central rotational stem and the stability of the implant. METHODS: The stem lengths and tapers of knee implants made by seven manufacturers were measured. The tilting laxity of each design was tested by measuring the degree of tilting of the central rotational stem within the tibial housing that occurred with increasing amounts of distraction. The maximum amount of distraction that was possible before the stem dislocated was determined for each design. RESULTS: Implant designs with a short and/or markedly tapered central rotational stem had the greatest tilting, laxity, and instability of that stem. The Howmedica, Techmedica, Intermedics/Sulzer Medica, and Wright Medical Technology/ Dow Corning Wright designs required > or = 39 mm of distraction before they dislocated. The Biomet knee implant required 33 or 44 mm of distraction to dislocate, depending on the thickness of the polyethylene tray that was utilized. The S-ROM knee required only 26 mm of distraction before dislocation occurred. CONCLUSIONS: The measurements confirmed that the shorter the stem and the greater its taper, the greater the instability and laxity at any given amount of joint distraction.