Scott E. Porter

Biomaterial developments for bone tissue engineering.

The development of bone tissue engineering is directly related to changes in materials technology. While the inclusion of materials requirements is standard in the design process of engineered bone substitutes, it is also critical to incorporate clinical requirements in order to engineer a clinically relevant device. This review presents the clinical need for bone tissue-engineered alternatives to the present materials used in bone grafting techniques, a status report on clinically available bone tissue-engineering devices, and recent advances in biomaterials research. The discussion of ongoing research includes the current state of osseoactive factors and the delivery of these factors using bioceramics and absorbable biopolymers. Suggestions are also presented as to the desirable design features that would make an engineered device clinically effective.

Complications of acetabular fracture surgery in morbidly obese patients.

Objectives: To compare the early complications with operative treatment of acetabular fractures in morbidly obese (body mass index ≥40) patients when compared with all other patients. Design: Retrospective review. Setting: University medical center. Patients/Participants: Four hundred thirty-five consecutive patients with acetabular fractures operatively treated by a single surgeon. Forty-one of these patients were morbidly obese (group 1) and were compared with the remaining patients (group 2). Group 2, therefore, included patients who were clinically overweight and obese. Intervention: Operative repair of acetabular fracture. Main Outcome Measurements: Outcome variables included patient positioning time, total operative time, estimated intraoperative blood loss, length of hospital stay, perioperative complications, and late complications. Results: The average total operative time was 293 minutes for group 1 and 250 minutes (P = 0.008) for group 2. The hospital stay for group 1 averaged 26 days versus 15 days in group 2 (P < 0.01). There were 19 (46%) wound complications in group 1 compared with 49 (12%) in group 2 (P < 0.0001). Overall, there were complications in 26 of the 41 patients (63%) in group 1 and in 96 of the 394 patients (24%) in group 2. Group 1s relative risk of having a complication was 2.6 (95% confidence interval = 2.4-2.8) when compared with group 2. Conclusions: Our morbidly obese population had a statistically higher complication rate, longer operative times, and greater estimated intraoperative blood loss. The majority of complications were related primarily to wound healing problems and successfully controlled with aggressive approach to surgical debridement.

Operative experience of pelvic fractures in the obese.

BackgroundDisruptions of the pelvic ring may be a significant short- or long-term source of morbidity and mortality. In the obese, temporary stabilization and definitive fixation of the injured pelvis is a much more difficult undertaking, requiring more surgeon expertise and larger surgical approaches. Complications that arise as a result of the operative fixation of pelvic ring injuries may significantly minimize any potential long-term benefits conferred by attempts at fixation.MethodsDuring a continuous 46-month period, 288 patients with pelvic ring injuries were prospectively enrolled into a database. A cohort of 186 nonobese patients (group 1) was compared to the cohort of 102 obese patients (group 2). Injury patterns were classified and outcome variables were grouped into perioperative variables, perioperative complications, and late complications.ResultsInjury patterns differed significantly between the two groups. There was an increase in the perioperative variables. Overall, there were complications in 19% of nonobese patients and 39% of obese patients (p < 0.001). Wound complications dominated in the obese group. There were 64 additional surgeries in 30 (16%) patients that were the direct result of complications in group 1 and 62 additional surgeries in 31 (31%) patients in group 2.ConclusionsIn the obese, the time commitment, postoperative complication rate, and subsequent surgery rate are significantly greater. In this patient population, special attention should be focused on operative and soft tissue techniques in an effort to lessen the infection risk, the most likely cause of morbidity.

The effect of age on gene expression in adult and juvenile rats following femoral fracture.

Objective To compare mRNA gene expression during fracture healing in young and adult rats. Design Gene expression was measured at zero, 1, 2, 4, 6, 8 and 10 weeks after fracture (6 rats/age/time point) in rats at 6 and 26 weeks of age at surgery. Setting AAALAC-accredited vivarium of an independent academic medical center. Animals Female Sprague-Dawley rats at 6 and 26 weeks of age. Intervention An intramedullary rod was placed retrograde in the left femur, and a simple transverse closed middiaphyseal fracture was induced. Main Outcome Measurements mRNA gene expression was measured for 34 genes for extracellular matrix, osteoblasts, bone morphogenic protein, inflammation, cytokine, and receptor genes. Results The young rats reached radiographic union by 4 weeks after fracture, whereas the adult rats took 8 to 10 weeks to unite. All genes studied increased in mRNA expression with a peak at 1 to 2 weeks after fracture. All genes in the young rats then subsided to baseline by 4 weeks after fracture. However, during the longer period needed for radiographic union in the adult rats, only genes related to bone matrix, osteoblastic markers, angiogenesis, and the fibroblast growth factors remained significantly up-regulated at 4 and 6 weeks after fracture. Genes related to cartilage, Indian hedgehog, the bone morphogenetic proteins, and transforming growth factor-&bgr; came to undetectable baseline values in the adult rats prior to radiographic union. Conclusions Most stimulators of bone healing are not expressed during the later stages of fracture repair in adult rats. Other genes must control bone growth to bridge the fracture gap.

Acetabular fracture patterns and their associated injuries

Objectives: Characterize relationships between acetabular fractures patterns and visceral organ injuries. Design: Retrospective review. Setting: University medical center. Patients/Participants: Three hundred twenty-three patients with displaced acetabular fractures identified in a prospectively maintained database. Intervention: Acetabular fractures were classified according to force vector at the time of injury. Posterior wall, posterior column, and posterior column/posterior wall injuries were assumed to have been caused by an axial load. The remaining seven acetabular fracture types were assumed to have resulted from a lateral or trochanteric load. Records were reviewed to establish any relationship between acetabular fracture patterns defined by their force vector and injuries to other skeletal and nonskeletal organ systems. Main Outcome Measurements: Comparison of organ injury end points of additional skeletal injury; bowel, bladder, brain, kidney, liver, spleen, and lung injury; retroperitoneal hematoma; and vascular injury of the pelvis. Data were analyzed using chi-square, with statistical significance defined as P < 0.05. Results: Acetabular fractures resulting from lateral loads had a statistically higher association with retroperitoneal hematomas (P < 0.001), spleen (P < 0.008), liver (P < 0.002), vascular (P < 0.001), kidney (P < 0.001), and bladder (P < 0.001) injuries than did posteriorly directed acetabular fractures. Transverse posterior wall fractures exhibited intermediate characteristics between axial load and the remaining lateral load patterns. Conclusions: Direction of force is important in the etiology of nonskeletal injury patterns. The possibility of additional nonskeletal injury increases from the rates seen in axial load patterns to those in lateral load patterns involving the anterior column.

Is Obesity Protective Against Wound Healing Complications in Pilon Surgery? Soft Tissue Envelope and Pilon Fractures in the Obese

Open treatment of pilon fractures is associated with wound healing complications. A traumatized, limited soft tissue envelope contributes to wound healing complications. Obese patients have larger soft tissue envelopes around the ankle, theoretically providing a greater area for energy distribution and more accommodation to implants. This led us to test 2 hypotheses: (1) ankle dimensions in obese patients are larger than in lean patients, and (2) the increased soft tissue envelope volume translates into fewer wound complications. A consecutive series of 176 pilon fractures treated from March 2002 to December 2007 were retrospectively reviewed. Inclusion criteria were adults who received a preoperative computed tomography (CT) scan and were treated with a staged protocol including plating. Patients with body mass index (BMI) >30 were compared to those with BMI <30 for CT-derived ankle dimensions and wound complications. Comorbidities were evaluated for their role as potential confounders. Thirty-one fractures in obese patients were compared to 83 in lean patients. The average ratio of bone area to soft tissue area at the tibial plafond was 0.35 for the obese group and 0.38 for the lean group (P=.012). There were 8 major wound-healing complications. Four occurred in the obese group (incidence 13%), and 4 in the lean group (incidence 5%) (P=.252). Ankle dimensions in clinically obese patients are larger than in lean patients. Obesity does not appear to be protective of wound-healing complications, but rather there is a trend toward the opposite.

Operative Fixation of Acetabular Fractures in the Pregnant Patient

Objective: To describe in utero radiation exposures in pregnant patients undergoing acetabular fracture repair. Design: Retrospective case series. Setting: University-affiliated regional trauma center. Patient/Participants: Eight pregnant patients with acetabular fractures treated over a 6-year period. There were an additional 518 acetabular fractures in nonpregnant patients treated during the same time period. Intervention: Open reduction and internal fixation of the acetabulum fracture. Outcome Measurements: None. This is a descriptive series reporting fetal radiation doses, fetal fluoroscopy exposure times, and fetal viability after treatment. Results: The gestational age of the fetuses at presentation ranged from 5 to 26 weeks. Infant delivery averaged 27 weeks from the time of surgery and all pregnancies reached 36 weeks. Apgar scores were normal each child including 1 twin delivery. There were 4 posterior wall fractures, 3 transverse or posterior wall fractures, and 1 posterior column fracture. Intraoperative pelvic fluoroscopy averaged 39 seconds. There were no operative complications and fracture reductions were anatomic in 7 patients. Computed tomography scan of the pelvis conferred the greatest exposure risk to the fetus and fluoroscopy conferred the least. In each case that required a computed tomography scan of the pelvis, the calculated radiation exposure dose to the fetus was greater than 5 cGy. Conclusions: The results of this study demonstrate that with a team approach and the judicious use of radiographic imaging during the surgical care of a displaced acetabular fracture in the pregnant patient, minimal risk to the baby can be achieved in pursuit of acceptable articular reductions.

The Clamshell Osteotomy: A New Technique to Correct Complex Diaphyseal Malunions

BACKGROUND The treatment of complex diaphyseal malunions is challenging, requiring extensive preoperative planning and precise operative technique. We have developed a simpler method to treat some of these deformities. METHODS Ten patients with complex diaphyseal malunions (including four femoral and six tibial malunions) underwent a clamshell osteotomy. The indications for surgery included pain at adjacent joints and deformity. After surgical exposure, the malunited segment was transected perpendicular to the normal diaphysis proximally and distally. The transected segment was again osteotomized along its long axis and was wedged open, similar to opening a clamshell. The proximal and distal segments of the diaphysis were then aligned with use of an intramedullary rod as an anatomic axis template and with use of the contralateral extremity as a length and rotation template. The patients were assessed clinically and radiographically at a mean of thirty-one months (range, six to fifty-two months) after the osteotomy. RESULTS Complete angular correction was achieved in each case; the amount of correction ranged from 2 degrees to 20 degrees in the coronal plane, from 0 degrees to 32 degrees in the sagittal plane, and from 0 degrees to 25 degrees in the axial plane (rotation). Correction of length ranged from 0 to 5 cm, and limb length was restored to within 2 cm in all patients. All osteotomy sites were healed clinically by six months. While no deep infections occurred, superficial wound dehiscence occurred in two patients along the approach for the longitudinal portion of the osteotomy, emphasizing the importance of careful soft-tissue handling and patient selection. CONCLUSIONS The clamshell osteotomy provides a useful way to correct many forms of diaphyseal malunion by realigning the anatomic axis of the long bone with use of a reamed intramedullary rod as a template. This technique provides an alternative that could decrease preoperative planning time and complexity as well as decrease the need for intraoperative osteotomy precision in a correctly chosen subset of patients with diaphyseal deformities.

Biomechanical analysis comparing titanium elastic nails with locked plating in two simulated pediatric femur fracture models.

Background: Increasing attention is being paid to the influences that the body habitus and weight of the pediatric patient impose upon the fixation methods for femur fractures. Of the widely accepted treatment options, little biomechanical or clinical data exist comparing flexible intramedullary nailing and locked plating. The aim of this study was to compare the mechanical stability of unstable pediatric diaphyseal femur fractures fixed with titanium flexible intramedullary nails or a titanium locking plate using a synthetic femur model. Methods: Fracture stabilization was carried out with either 4.0-mm titanium elastic nails or 16-hole 4.5-mm narrow titanium locking compression plates. Axial and rotational testing of each specimen was performed. The axial loading rate was 0.20 mm/s. The torsional loading rate was 0.1 degrees rotation per second. The axial compressive modulus was defined as the compressive stress divided by the compressive strain. The rotational stiffness was defined as the torque moment applied to the femoral head divided by the resulting rotational displacement (in radians). The yield point or load to failure of the simulated fracture constructs was recorded for each specimen. Results: The modulus for comminuted fractures measured during the application of axial compression was 0.657 GPa for plate constructs and 0.326 GPa for elastic nail constructs (P=0.021). The modulus for oblique fractures during axial loading treated with plate fixation or titanium elastic nails was 1.63 and 0.466 GPa, respectively (P<0.0001). The yield point for comminuted fractures occurred at an axial load of 2304.7 N (SD±315.77) for plate constructs and 383.6 N (SD±139.2) for elastic nail constructs (P<0.001). For oblique fractures, the yield load occurred at 3111.9 N (SD±821.9) for plate constructs and at 1367.0 N (SD±98.9) for elastic nail constructs (P<0.0001). Conclusions: Locked plating provides a biomechanically more stable construct than elastic intramedullary nailing. Its use as part of the technique of indirect reduction and submuscular plating remain a viable alternative in the treatment of length-unstable pediatric femur fracture patterns. Clinical Relevance: Provide biomechanical evidence supporting the use of plating techniques in the pediatric femur fracture population.

Acetabular fracture reductions in the obese patient.

Objectives: To evaluate the radiographic and computed tomographic reduction qualities after acetabular fracture repair in obese and nonobese patients. Design: Retrospective review. Setting: University medical center. Patients/Participants: Two hundred forty-two patients were treated with open reduction internal fixation for displaced acetabular fractures. The nonobese group (Group 1) consisted of 149 patients and the obese group (Group 2) had 93 patients. A nonmorbidly obese group (Group 3 = 221 patients) and a morbidly obese group (Group 4 = 21 patients) were also created from the same patient population. Intervention: Operative repair of acetabular fractures. Main Outcome Measurements: Reductions on postoperative radiographs were classified as anatomic with less than 1 mm, imperfect with 2 to 3 mm, and poor with greater than 3 mm of residual displacement. On postoperative computed tomographic scans, reductions were considered nonanatomic with persistent gap or step displacements greater than or equal to 2 mm. Results: Anatomic radiographic reductions were achieved in 72% of the nonobese patients, 70% of the obese patients, 72% of the nonmorbidly obese patients, and 61% of the morbidly obese patients. (P = 0.379) On postoperative computed tomographic scans, an acceptable reduction was obtained in 47% of the nonobese patients, 44% of the obese patients, 47% of the nonmorbidly obese patients, and 31% of the morbidly obese patients. (P = 0.232). Conclusions: Anatomic or satisfactory reductions can be similarly achieved in all classes of nonmorbidly obese patients who have sustained displaced acetabular fractures. In the morbidly obese, anatomic reductions may be more difficult to obtain.