Demographics and Clinical Presentation of Early-Stage Legg-Calvé-Perthes Disease: A Prospective, Multicenter, International Study.

BACKGROUND: Children with Legg-Calvé-Perthes disease (LCPD) are classically described as small, thin, high-energy children presenting with a painless limp. Epidemiologic studies have historically been retrospective and regional in nature. The purpose of this study was to determine the demographic and clinical features of children presenting in the early stages of LCPD in an international, multicenter cohort. METHODS: Children (6 to 10 years) in the early stages of LCPD (modified Waldenström stage I to IIa) were enrolled in a prospective, multicenter study. Demographic and clinical data at presentation were analyzed. Body mass index percentiles were determined using country-specific growth charts for children in the United States and India, two countries with largest enrollment. Statistical analyses included t-tests and chi-square. RESULTS: A total of 209 children (86% males; mean age 7.9 ± 1.2 years) from 25 centers (six countries) were included. Eight-four percent of children presented with pain with or without a limp. Average pain score at presentation was 3 ± 2 (range 0 to 9), and 63% of children (n = 105) used pain medications. Of these children 65% required medication more than once per week. Thirty percent of children missed school due to pain in the past month, and of those, 74% missed at least 1 day per week. Twenty-nine percent of children from the United States and 20% of children from India were overweight or obese. Nineteen percent reported household smoking. DISCUSSION: This prospective study provides a new international multicenter representation of early LCPD. The frequency of pain and missed school highlights the substantial morbidity and potential social cost and burden for children and families. The prevalence of being overweight/obese in our LCPD cohort was comparable to rates within the pediatric cohort as a whole, and fewer children have a history of smoke exposure than in previous reports. LEVEL OF EVIDENCE: Level II, prospective comparative study.

Reproducibility of Radiographic Measurements Made in the Active Stages of Legg-Calvé-Perthes Disease: Evaluation of a Prognostic Indicator and an Interim Outcome Measure.

BACKGROUND: Deformity index (DI) and extrusion index (EI) are 2 radiographic methods currently used to quantify femoral head deformity in the active stages of Legg-Calvé-Perthes disease. This study aimed to quantify the interobserver reproducibility of the 2 methods using a large, international group of pediatric orthopaedic surgeons with diverse clinical experience. METHODS: Radiographs of patients (age 6 to 11 y at time of diagnosis) prospectively enrolled in an international multicenter-cohort study, were measured by members of our study group. For each radiograph, the raters independently assessed EI (n=33 cases) and DI (n=32 cases), along with the rater's subjective assessment of the extent of hip deformity (ie, none, mild, moderate, or severe). Reliability analysis was conducted using intraclass correlation coefficient (ICC) and κ techniques. RESULTS: The ICC for EI on the affected side was 0.68 (95% confidence interval: 0.57-0.79). The calculated DI ICC was 0.53 (95% confidence interval: 0.41-0.68). Subjectively, an average of 68±3.5% of surgeons agreed on the subjective description of each patient's femoral head deformity. CONCLUSIONS: EI is measured with a reasonably high rate of correlation among surgeons from disparate backgrounds. Agreement is lower among the same group of surgeons when the more complex DI is used. DI is most useful when utilized by a small number of experienced observers in a research setting, whereas EI may have better clinical applicability. LEVEL OF EVIDENCE: Level III-reliability study.

Reliability of the modified lateral pillar classification for Legg Calvé Perthes disease performed by a large group of international paediatric orthopaedic surgeons.

PURPOSE: The modified lateral pillar classification (mLPC) is used for prognostication in the fragmentation stage of Legg Calvé Perthes disease. Previous reliability assessments of mLPC range from fair to good agreement when evaluated by a small number of observers with pre-selected radiographs. The purpose of this study was to determine the inter-observer and intra-observer reliability of mLPC performed by a group of international paediatric orthopaedic surgeons. Surgeons self-selected the radiograph for mLPC assessment, as would be done clinically. METHODS: In total, 40 Perthes cases with serial radiographs were selected. For each case, 26 surgeons independently selected a radiograph and assigned mLPC and 21 raters re-evaluated the same 40 cases to establish intra-observer reliability. Rater performance was determined through surgeon consensus using the mode mLPC as 'gold standard'. Inter-observer and intra-observer reliability data were analysed using weighted kappa statistics. RESULTS: The weighted kappa for inter-observer correlation for mLPC was 0.64 (95% confidence interval: 0.55 to 0.74) and was 0.82 (range: 0.35 to 0.99) for intra-observer correlation. Individual surgeon's overall performance varied from 48% to 88% agreement. Surgeon mLPC performance was not influenced by years of experience (p = 0.51). Radiograph selection did not influence gold standard assignment of mLPC. There was greater agreement on cases of mild B hips and severe C hips. CONCLUSIONS: mLPC has low good inter-observer agreement when performed by a large number of surgeons with varied experience. Surgeons frequently chose different radiographs, with no impact on mLPC agreement. Further refinement is needed to help differentiate hips on the border of group B and C. LEVEL OF EVIDENCE: III.

Is nonoperative treatment of pediatric type I open fractures safe and effective?

PURPOSE: There is limited literature on nonoperative treatment of open type I pediatric fractures. Our purpose was to evaluate the rate of infection in pediatric patients with type I open fractures treated nonoperatively at our institution without admission from the emergency department (ED). METHODS: We performed a retrospective chart review of all patients who sustained a type I open fracture of the forearm or tibia from 2000 through 2013. Forty patients fit the inclusion criteria: <18 years old with type I open fracture treated nonoperatively with irrigation and debridement, followed by closed reduction and casting of the fracture under conscious sedation in the ED. All patients were discharged home. The primary outcome was presence of infection. Secondary outcomes included occurrence of a delayed union, time to union, complications, and residual angulation. RESULTS: There were no reported or documented infections. There was one case of a retained foreign body (<1 cm) in a mid-diaphyseal forearm fracture, which was removed in clinic at 4 weeks after the patient developed a granuloma with no infectious sequela. There was one case of a delayed union; all patients eventually had complete bony union. There was minimal residual angulation in both upper and lower extremities at last follow-up. CONCLUSIONS: Nonoperative treatment of type I open fractures in pediatric patients can be performed safely with little risk of infection. This preliminary evidence may serve as a foundation for future prospective studies.

Transfemoral amputations: is there an effect of residual limb length and orientation on energy expenditure?

BACKGROUND: Energy cost of ambulation has been evaluated using a variety of measures. With aberrant motions resulting from compensatory strategies, persons with transfemoral amputations generally exhibit a larger center of mass excursion and an increased energy cost. However, few studies have analyzed the effect of residual femur length and orientation or energy cost of ambulation. QUESTIONS/PURPOSES: The purpose of this study was to compare residual limb length and orientation with energy efficiency in patients with transfemoral amputation. We hypothesized that patients with shorter residual limbs and/or more abnormal residual femur alignment would have higher energy expenditure cost and greater center of mass movement than those with longer residual limbs resulting from lacking musculature, shorter and/or misoriented lever arms, and greater effort required to ambulate through use of compensatory movements. METHODS: Twenty-six adults with acute, trauma-related unilateral transfemoral amputations underwent gait and metabolic analysis testing. Patients were separated into groups for analysis based on residual limb length and residual femoral angle. RESULTS: Cohorts with longer residual limbs walked faster than those with shorter residual limbs (self-selected walking velocity 1.28 m/s versus 1.11 m/s, measured effect size = 1.08; 95% confidence interval = short 1.10-1.12, long 1.26-1.30; p = 0.04). However, there were no differences found with the numbers available between the compared cohorts regardless of limb length or orientation in regard to O2 cost or other metabolic variables, including the center of mass motion. CONCLUSIONS: Those with longer residual limbs after transfemoral amputation chose a faster self-selected walking velocity, mirroring previous studies; however, metabolic energy and center of mass metrics did not demonstrate a difference in determining whether energy expenditure is affected by length or orientation of the residual limb after transfemoral amputation. These factors may therefore have less effect on transfemoral amputee gait efficiency and energy requirements than previously thought.

Transfemoral amputations: the effect of residual limb length and orientation on gait analysis outcome measures.

BACKGROUND: The level of function achieved following a transfemoral amputation is believed to be affected by surgical attachment of the remaining musculature, resulting orientation of the femur, residual limb length, and eventual prosthetic fit. METHODS: Twenty-six subjects underwent gait analysis testing in the current preferred prosthesis more than twenty-four months postamputation. The femoral length and orientation angles of each subject were measured from standing postoperative radiographic scanograms. The subjects were separated into groups for analysis on the basis of the femoral shaft angles and the residual limb length ratios. Gait analysis was performed to collect kinematic and temporospatial parameters. RESULTS: A good correlation was observed between residual femoral length and trunk with regard to forward lean (r = -0.683) and lateral flexion (r = -0.628). A good correlation was also observed between residual femoral length and pelvic motion with regard to pelvic tilt (r = -0.691) and obliquity (r = -0.398). A moderate correlation was observed with speed (r = 0.550), indicating that subjects with shorter residual limbs experienced a greater excursion in the torso and pelvis, while walking at a slower self-selected pace. A significant correlation (r = 0.721, p < 0.001) was observed between the femoral shaft abduction angle and the residual femoral length; the shorter the residual limb, the more abducted it was. CONCLUSIONS: The length of the residual femur substantially influences temporospatial and kinematic gait outcomes following transfemoral amputation, and appears to be more important than femoral orientation with regard to these parameters.

Early onset scoliosis: modern treatment and results.

BACKGROUND: Early onset scoliosis (EOS) is a potentially fatal, challenging group of diseases the management of which has markedly changed in the last decade. The purpose of this review is to provide the reader with a brief description of each of these new therapeutic modalities, their indications for use, and early clinical results. METHODS: A systematic review of peer-reviewed publications and abstracts related to the treatment of EOS in the last decade was carried out and synthesized into a review of modern treatment methods. RESULTS: Recent advances in techniques and understanding of preserving the thoracic space have improved the morbidity and mortality of children with progressive EOS. Derotational casting may be used in younger patients with curves between 25 and 60 degrees. The vertical expandable prosthetic titanium rib is best suited for patients with thoracic insufficiency syndrome. Single or dual growing rods may be used alone or in combination with vertical expandable prosthetic titanium rib to treat patients with progressive EOS who are not candidates for casting. Shilla technique is an alternative to growing rods that avoids the morbidity of repeated lengthenings but is not as well proven as the techniques described above. Other methods such as automatic growing rods and growth modulation techniques are still investigational, and their role needs to be defined after further study. CONCLUSIONS: Recent advances have improved the treatment of children with EOS. Treatment continues to be challenging with complication rates higher than treatment of idiopathic scoliosis. LEVEL OF EVIDENCE: Level V.

Spica casting for pediatric femoral fractures: a prospective, randomized controlled study of single-leg versus double-leg spica casts.

BACKGROUND: At many centers, double-leg spica casting is the treatment of choice for diaphyseal femoral fractures in children two to six years old. We hypothesized that such patients can be effectively treated with single-leg spica casting and that such treatment would result in easier care and better patient function during treatment. METHODS: In a prospective, randomized controlled study, fifty-two patients two to six years old with a diaphyseal femoral fracture were randomly assigned to be treated immediately (after consent was obtained) with a single-leg (twenty-four patients) or double-leg (twenty-eight patients) spica cast. Serial radiographs were evaluated for maintenance of fracture reduction with respect to limb length, varus/valgus angulation, and procurvatum/recurvatum angulation. After cast removal, the performance version of the Activities Scale for Kids questionnaire and a custom-written survey were administered to the parents so that they could evaluate the ease of care and function of the children during treatment. Means were compared between treatment groups with use of Student t tests. P values of <0.05 were considered significant. RESULTS: All limbs healed in satisfactory alignment. The children treated with a single-leg spica cast were more likely to fit into car seats (p < 0.05) and fit more comfortably into chairs (p < 0.05). Caregivers of patients treated with a single-leg cast took less time off work (p < 0.05). There were no major complications. CONCLUSIONS: Treatment of pediatric femoral fractures with a single-leg spica cast is effective and safe, and postfracture patient care is facilitated. LEVEL OF EVIDENCE: Therapeutic Level I. See Instructions for Authors for a complete description of levels of evidence.

Short-term results of arthroscopic treatment of osteochondritis dissecans in skeletally immature patients.

BACKGROUND: Osteochondritis dissecans (OCD) of the capitellum occurs in skeletally immature athletes, and most likely results from repetitive trauma during overhead activities. Treatment may consist of activity modifications, internal fixation, abrasion chondroplasty, microfracture, antegrade drilling, retrograde drilling, osteochondral autograft or allograft implantation, chondrocyte implantation, and rib autograft through arthroscopy or arthrotomy. One treatment modality has not been proven to be clearly more effective than the others. This study was undertaken to evaluate our treatment regimen that utilized arthroscopic-assisted treatments of capitellar OCD, including removal of loose bodies, antegrade or retrograde drilling, and chondroplasty in the pediatric population. METHODS: All patients treated arthroscopically for a diagnosis of capitellar OCD over a 5-year period, were retrospectively reviewed. All were asked to return for follow-up questionnaire and radiographs. Exclusion criteria included those lost to follow-up. Demographics were recorded and range of motion was evaluated preoperatively and at most recent follow-up for flexion, extension, supination, and pronation. Preoperative and the most recent anterior/posterior and lateral radiographs of the elbow were reviewed. A 200-point elbow rating scale was used to assess patient outcomes. The arthroscopic appearance of the lesion was graded. Changes in preoperative to postoperative range of motion and size of lesion were compared using repeated measures analysis of variation. RESULTS: There were 13 elbows in 12 patients; only 3 of the injuries occurred acutely. Mean age at the time of surgery was 13.1±1.07 (range, 10.8 to 14.6 y). Mean follow-up was 23.4±16.7 months (range, 2 to 60 mo). There were 3 grade I lesions, 2 grade II lesions, 1 grade IV lesion, and 7 grade V lesions. Seven of the lesions underwent transhumeral drilling, 2 transarticular drilling, 3 loose body removals, and 2 had only debridement. There were no postoperative infections or neurovascular injuries. Three of the elbows (20%) required eventual arthrotomy at a mean of 27.9 months after the index procedure. At final follow-up, 67% reported no pain and 33% reported occasional pain. No patients reported any swelling. Eighty-three percent reported no locking or catching and 17% reported occasional locking or catching. No patients reported any activity restrictions. The mean subjective score was 96±6 of 100 and the mean objective score was 100 of 100. Mean extension improved significantly from -17 to -7 degrees (P<0.001). CONCLUSIONS: Treatment of children with OCD lesions of the capitellum with arthroscopic-assisted debridement and fenestration of the sclerotic rim (trans-humeral if overlaying cartilage is intact), plus fixation of the overlaying cartilage if not securely attached to the subchondral bone permits the return to physical activity, but may not allow return to the injury-inducing sport. Our short-term outcomes obtained using this regimen found this technique to be safe and reliable, but other interventions may be required if continued disability persists.

Enhanced biomechanical stiffness with large pins in the operative treatment of pediatric supracondylar humerus fractures.

BACKGROUND: Various pin configurations have been recommended for the treatment of supracondylar humerus fractures on the basis of the choice between stability versus the risk of iatrogenic nerve injury. However, little attention has been paid to pin size. The purpose of this study was to evaluate the stability of large (2.8 mm or 0.110 inch) and small (1.6 mm or 0.062 inch) pin constructs in 6 configurations. METHODS: A transverse fracture pattern was created by sectioning synthetic humeri in the midolecranon fossa. The specimens were then reduced and pinned in one of 6 configurations: 2 small pins (Kirschner wires) placed crossed or lateral divergent, 2 large pins (Steinmann pins) placed crossed or lateral divergent, or 3 small pins placed crossed or lateral divergent. All specimens were then tested in sagittal extension bending. We investigated the effect of pin configuration and cycle on the sagittal stiffness using multiple linear regression. RESULTS: The 2 small lateral divergent pin configuration was significantly less stable than small crossed pins and large pins in a crossed or a lateral configuration. The addition of a third (lateral) pin to the small crossed pin construct made it significantly less stable than 2 large crossed pins. Although the stability between the remaining configurations was not significantly different, the 2 large crossed pins required the greatest torque to rotate the fragment 20 degrees. There was a significant reduction in torque as a function of cycle, suggesting a loss of fixation during cycling (P<0.05). CONCLUSIONS: Large pins (2.8 mm) in any configuration and the placement of small pins (1.6 mm) in a crossed configuration provided more stable reduction in sagittal extension bending than did the conventional 2 small pins in a lateral divergent pin configuration. The most stable configurations involve crossing the medial and lateral pins. CLINICAL RELEVANCE: There are more stable options than the traditional 2 small lateral pin configuration for fixation of unstable supracondylar fractures. The addition of a third pin is not always advantageous.

Adolescent idiopathic scoliosis treated with open instrumented anterior spinal fusion: five-year follow-up.

STUDY DESIGN: A multicenter prospective database was queried for patients who underwent open instrumented anterior spinal fusion (OASF) for treatment of primary thoracic (Lenke 1) adolescent idiopathic scoliosis (AIS). OBJECTIVES: To present the intermediate radiographic and pulmonary function testing (PFT) data from patients who underwent OASF using modern, rigid instrumentation. SUMMARY OF BACKGROUND DATA: Anterior spinal fusion is an excellent method to correct the 3-dimensional deformity produced by AIS. Modern instrumentation consisting of stronger metals, unthreaded rods, and dual rod systems should theoretically decrease the incidence of rod breakage, pseudarthrosis, and loss of correction seen in earlier OASF studies. The paucity of intermediate and long-term data prevents surgeons and patients from making an informed decision regarding the true incidence of these complications. METHODS: Of 101 potential patients who underwent OASF with a minimum 5-year follow-up, 85 (85%) were studied. Standing radiographs were analyzed before surgery and at first standing erect, 2-year, and 5-year follow-up. PFT data were collected before surgery and at 5 years after surgery. RESULTS: Complete 5-year follow-up was obtained in 85 patients. Five years after surgery, the mean coronal correction was 26 degrees (51%; P < 0.05) and the thoracolumbar/lumbar curve improved 16 degrees (51%). There was a 9-degree (P < 0.001) increase in kyphosis, and there were 9 patients (11%) in whom the C7 plumb line translated >2 cm. There was a 6.7% decrease in predicted FEV1 over the 5-year period, from 75.5% +/- 13% before surgery to 68.8% +/- 2% at 5-year follow-up (P = 0.007); however, there was no significant change in FVC. There were 3 significant adverse events: 1 implant breakage requiring reoperation and 2 cases of progression of the main thoracic curve requiring reoperation. CONCLUSION: OASF is a reproducible and safe method to treat thoracic AIS. It provides good coronal and sagittal correction of the main thoracic and compensatory thoracolumbar/lumbar curves that is maintained with intermediate term follow-up. In skeletally immature children, this technique can cause an increase in kyphosis beyond normal values, and less correction of kyphosis should be considered during instrumentation. As with any procedure that employs a thoracotomy, pulmonary function is mildly decreased at final follow-up.

A biomechanical comparison of different types of lumbopelvic fixation.

STUDY DESIGN: Comparative biomechanical testing in calf spines. OBJECTIVE: To biomechanically evaluate 4 techniques of lumbosacral fixation. SUMMARY OF BACKGROUND DATA: Pelvic fixation is a problematic area, and currently, the preferred method of pelvic fixation is controversial. Clinically, iliac screws have demonstrated decreased rod breakage rates, and better correction of pelvic obliquity than unthreaded rods (Galveston technique), but several modern methods of iliac fixation have not been compared. METHODS: A total of 32 male calf spines were tested under axial rotation, flexion/extension, and lateral bending. Following intact testing, specimens were instrumented in the following groups: group 1-Modified Galveston technique with rods connected directly to iliac screws (no S1 fixation); group 2-S1 screws and iliac screws with offset connectors distal to S1; group 3-S1 screws and iliac screws with offset connectors coupled to the longitudinal rod between L6 and S1; and group 4-S1 and S2 screws without iliac fixation. Pedicle screws were placed from L3 to L6. Following nondestructive testing, specimens were fixed at the cephalad aspect of the construct and flexed to failure, with peak failure moment (Nm). RESULTS: Group 1 demonstrated significantly more flexion/extension than groups 2, 3, 4 (P<0.001). There were no significant differences between groups for lateral bending or axial rotation at L3-S1 or L6-S1. During destructive testing, group 4 showed a significant reduction in peak failure compared to group 1 (P<0.001), group 2 (P=0.001), and group 3 (P<0.001). There was no significant difference between groups 1, 2, and 3 and all specimens failed at the distal fixation. CONCLUSION: With extension of instrumentation across the lumbosacral junction, our results indicate significant improvement in stability with the use of S1 screws and iliac screw fixation. Furthermore, there does not appear to be any significant difference in the location of the connector for the iliac screw.

Contralateral structural femoral autograft use in treatment of an open periarticular knee fracture to perform knee arthrodesis.

Combat-related blast injuries often cause devastating extremity trauma. We report a case of a 21-year-old male service member who sustained massive bilateral lower extremity trauma secondary to a blast injury. His orthopaedic injuries included a near traumatic disarticulation of the right knee and a left open type IIIB periarticular knee fracture with traumatic patellectomy, loss of the extensor mechanism, and segmental loss of the distal 11 cm of his femur. Definitive treatment of his injuries included a contralateral structural cortical femoral autograft which was implanted into the left knee segmental defect to facilitate knee fusion with an intramedullary knee fusion nail and a right transfemoral amputation. Radiographic evidence of solid fusion was obtained 8 months postoperatively. Currently, the patient is a community ambulator with the aid of his right lower extremity prosthetic limb and cane.

Correlation of residual limb length and gait parameters in amputees.

There is a lack of objective data on acceptable transection levels for transfemoral amputation. We retrospectively correlated the residual limb length of 13 young, athletic transfemoral and knee disarticulation amputees with temporal-spatial, kinematic, and kinetic outcomes after gait analysis. It was hypothesised that shorter residual limb lengths would correlate with greater gait deviations. Patients' residual femoral lengths ranged from 57% to 100% of their intact femoral length. With the exception of one patient, pelvic tilt excursion was inversely related to residual limb length. Limb length did not significantly correlate with any other temporal-spatial, kinematic, or kinetic parameter investigated. Consequently, these results suggest that if the femur is at least 57% of the length of the contralateral femur, length does not dramatically alter gait. This implies that surgeons may have more flexibility to amputate at a higher level to preserve soft tissue quality and improve prosthetic fitting without sacrificing gait function.

Low-intensity pulsed ultrasound does not enhance distraction callus in a rabbit model.

Low-intensity pulsed ultrasound has been reported to have a positive effect when applied during the consolidation phase of distraction osteogenesis and bone transportation, but the optimal application time has not been determined. We used a rabbit model to determine whether low-intensity pulsed ultrasound applied during the distraction and early consolidation phases of tibial lengthening would have a positive effect on regenerated bone formation. Radiographic analysis showed no differences in regenerated callus area or in percent of callus mineralization between treated and control tibias immediately after distraction or at 1, 2, or 3 weeks after distraction. Similarly, we observed no differences in structural stiffness or maximal torque to failure at 1.5 or 3 weeks after distraction. We detected no differences in bone mineral appositional rates or percent tissue composition measured histologically between groups. Our data do not support the application of low-intensity pulsed ultrasound to regenerated bone during distraction osteogenesis.

Complications associated with multiple, sequential osteotomies for children with cerebral palsy.

Children with cerebral palsy often require multiple, major reconstructive procedures. The purpose of this study was to evaluate whether multiple, major surgeries could be performed in a single setting with an acceptable complication rate. The medical records of 94 patients with a diagnosis of cerebral palsy operated on between the dates of 1993 and 1997 were reviewed. Patients were followed for a mean of 44.9+/-1.92 months. The average number of procedures per surgical session was 3.63+/-0.09 and the most common procedure performed was osteotomy of the proximal femur. The major complication rate was 24.4%. This institution's experience indicates that performance of multiple major bony procedures in one session is complicated but safe, and can be done with acceptable blood loss, infection rates and recurrence rates in a modern, multidisciplinary setting dedicated to the care of severely disabled children.

Effect of pulsed electromagnetic fields on maturation of regenerate bone in a rabbit limb lengthening model.

To study the effect of applying pulsed electromagnetic fields (PEMF) during the consolidation phase of limb lengthening, a mid-tibial osteotomy was performed in 18 adult New Zealand White rabbits and an external fixator was applied anteromedially. Animals were randomly assigned to treatment and control groups. After a 7-day latency period, the tibiae were distracted 0.5 mm every 12 h for 10 days. The treatment group received a 20-day course of PEMF for 60 min daily, coinciding with initiation of the consolidation phase. The control group received sham PEMF. Radiographs were performed weekly after distraction. Animals were euthanized 3 weeks after the end of distraction. Radiographic analysis revealed no significant difference in regenerate callus area between treatment and control tibiae immediately after distraction, at 1 week, 2 weeks, or 3 weeks after distraction ( p = 0.71, 0.22, 0.44, and 0.50, respectively). There was also no significant difference in percent callus mineralization ( p = 0.96, 0.69, 0.99, and 0.99, respectively). There was no significant difference between groups with respect to structural stiffness ( p = 0.80) or maximal torque to failure ( p = 0.62). However, there was a significant positive difference in mineral apposition rate between groups during the interval 1-2 weeks post-distraction ( p < 0.05). This difference was no longer evident by the interval 2-3 weeks post-distraction. While PEMF applied during the consolidation phase of limb lengthening did not appear to have a positive effect on bone regenerate, it increased osteoblastic activity in the cortical bone adjacent to the distraction site. Since the same PEMF signal was reported to be beneficial in the rabbit distraction osteogenesis when applied during distraction phase and consolidation phase, application of PEMF in the early phase may be more effective. Further work is necessary to determine optimal timing of the PEMF stimulation during distraction osteogenesis.

Quantification of the microstructural anisotropy of distraction osteogenesis in the rabbit tibia.

A longitudinal orientation of fibers and trabeculae has been observed histologically within distracted callus. This study quantified the intensity and angle of orientation of trabeculae within a distracted callus. Sixteen New Zealand white rabbits underwent unilateral tibial callus distraction with an external fixator across a mid-diaphyseal osteotomy. Included were: a seven-day postoperative latency period, ten days of distraction at 0.5 mm every 12 hours, and 20 days of post-distraction consolidation before euthanasia. Tibiae were removed, stripped of soft tissue, sectioned, and processed for decalcified histology. Micrographs of mid-coronal sections of the callus were evenly divided into 12 regions and underwent Fast Fourier Transform (FFT) analysis of the digitized image to determine the angle and intensity of the orientation of the bony trabeculae within the callus. The microstructure of the regenerate callus demonstrated an angle of orientation that uniformly matched that of cortical bone in all of regions of the callus and an intensity of orientation which approached that of cortical bone.