J G Craig

Computed tomographic assessment of fractures of the posterior wall of the acetabulum after operative treatment.

Background: The purpose of this study was to evaluate the results after operative treatment of fractures of the posterior wall of the acetabulum in relationship to the quality of the fracture reduction as assessed by postoperative two-dimensional computed tomography. Methods: The functional results for sixty-seven patients who had open reduction and internal fixation of an unstable fracture of the posterior wall of the acetabulum and the findings of two-dimensional computed tomography performed postoperatively were analyzed. Sixty-one patients were followed for a mean of four years after the injury, and the remaining six patients who had poor early results necessitating reconstructive surgery were followed for less than two years. All patients were evaluated preoperatively and postoperatively with use of three standard plain radiographs (one anteroposterior and two Judet 45° oblique pelvic radiographs) and a two-dimensional computed tomography scan. The functional outcome for the patients was evaluated with use of a modification of the clinical grading system described by Letournel and Judet. The radiographs were graded according to the criteria described by Matta. The two-dimensional computed tomography scans were used to determine fracture gap and offset measurements. Results: The clinical outcome was graded as excellent in thirty-one patients (46%), very good in twenty (30%), good in eight (12%), and poor in eight (12%). The final radiographic results were graded as excellent in fifty-three hips (79%), good in four (6%), fair in three (5%), and poor in seven (10%). There was a strong association between clinical outcome and final radiographic grade. Fracture reductions were graded as anatomic in sixty-five and imperfect in two, as determined with use of plain radiography. However, postoperative computed tomography revealed an incongruency (offset) of >2 mm in eleven hips and fracture gaps of ≥2 mm in fifty-two. Fracture gaps of ≥10 mm in any dimension or a total gap area of ≥35 mm 2 were associated with a poor result. The main risk factors for a poor result were a residual fracture gap width of ≥10 mm and osteonecrosis of the femoral head. Conclusions: The degree of residual fracture displacement is detected more accurately on postoperative computed tomography scans than on plain radiographs. The accuracy of surgical reduction as assessed on postoperative computed tomography is highly predictive of the clinical outcome. Level of Evidence: Therapeutic study, Level III-2 (retrospective cohort study). See Instructions to Authors for a complete description of levels of evidence.

Radiographic and CT Evaluation of Recombinant Human Bone Morphogenetic Protein-2–Assisted Spinal Interbody Fusion

OBJECTIVEnBone morphogenetic proteins BMPs, when used in spinal fusion, hasten healing and initiate distinct imaging features. We undertook a study to record and analyze the radiographic and CT changes after the use of recombinant human bone morphogenetic protein-2 (rhBMP-2) in spinal fusion surgery.nnnMATERIALS AND METHODSnThis study included 95 patients who underwent spinal interbody fusion using rhBMP-2. The lumbar spine fusion cohort consisted of 23 patients who underwent anterior lumbar interbody fusion, 36 patients who underwent transforaminal lumbar interbody fusion, and two patients who underwent posterior lumbar interbody fusion. The remaining 34 patients underwent anterior cervical decompression and fusion.nnnRESULTSnA polyetheretherketone cage was used as an interbody spacer in 59 patients (82 levels) and an allograft bone was the spacer in 36 patients (55 levels). Patients were evaluated 2 and 6 weeks after the procedure and then 3, 6, 12, and 24 months after the procedure. All patients underwent radiography at every follow-up visit, and CT evaluation was performed in 32 patients.nnnCONCLUSIONnFeatures observed on imaging that we attributed to the use of rhBMP-2 included an enhanced fusion rate and an increased incidence of prevertebral soft-tissue swelling in patients who underwent cervical fusion. Endplate resorption was observed in 100% of patients who underwent cervical fusion and in 82% of the lumbar levels. Subsidence of the cage resulting in narrowing of the disk space was seen in more than 50% of cases. Cage migration and heterotopic bone formation in the spinal canal and neural foramen occurred maximally in the lumbar spine of patients in whom a polyetheretherketone cage was placed using a transforaminal approach.

Evaluation of intraoperative nerve-monitoring during insertion of an iliosacral implant in an animal model.

BACKGROUNDnThe use of continuous electromyographic and somatosensory-evoked-potential monitoring systems has been advocated to assist in avoiding nerve-root injury during operations on the pelvic ring. More recently, it was suggested that stimulus-evoked electromyographic monitoring may further decrease the risk of iatrogenic nerve-root injury during posterior pelvic fixation by enabling the surgeon to determine the actual distance of an implant from a nerve root. The purpose of the current study was to evaluate the relative efficacy of these three methods of monitoring for minimizing the risk of neural injury during the placement of iliosacral implants.nnnMETHODSnWhile the function of the first sacral nerve root was monitored with the use of stimulus-evoked electromyographic, continuous electromyographic, and somatosensory-evoked-potential monitoring techniques, a 2.0-millimeter stainless-steel Kirschner wire was progressively inserted, guided by a high-speed computerized tomographic scanner, into the first sacral body of seventeen hemipelves in nine dogs. The end point was contact with the nerve as demonstrated by the computerized tomographic images. It was expected that this end point would be heralded by a burst of spontaneous electromyographic activity and an abnormal somatosensory-evoked-potential signal. Anatomical dissection at the completion of the study documented the final position of the Kirschner wire.nnnRESULTSnAnatomical dissection demonstrated compression or penetration of the nerve root in sixteen of the seventeen specimens. A spontaneous burst of electromyographic activity was not recorded for any specimen on continuous electromyographic monitoring; this finding was significantly different from what had been expected (p<0.001). Because of technical problems, somatosensory evoked potentials could be recorded for only twelve hemipelves that had nerve-root compression or penetration, and abnormal somatosensory evoked potentials were recorded for only one of the twelve; this finding was significantly different from what had been expected (p<0.001). A total of 113 stimulus-evoked electromyographic data points were obtained. The correlation coefficient for the relationship between the current threshold recorded with stimulus-evoked electromyographic monitoring and the distance of the wire from the nerve was 0.801 (p<0.001). The actual measured current thresholds were of an observed proportion not different from what had been expected (p = 0.48).nnnCONCLUSIONSnContinuous electromyographic and somatosensory-evoked-potential monitoring techniques failed to indicate contact with the nerve root reliably in this animal model. However, stimulus-evoked electromyographic monitoring consistently provided reliable information indicating the proximity of the implant to the nerve root.