Induced hypothyroidism alters articular cartilage in skeletally immature miniature swine

PURPOSE/AIM

Thyroid hormone has been implicated in the normal growth and development of articular cartilage; however, its effect on a disease state, such as hypothyroidism, is unknown. The purpose of this investigation was to compare normal articular cartilage from proximal femurs of immature miniature swine to proximal femurs from hypothyroid-induced immature miniature swine.

MATERIALS AND METHODS

Two 11-week-old male Sinclair miniature swine were made hypothyroid by administration of 6-propyl-2-thiouracil (PTU) in their drinking water; two control animals did not receive PTU. At 25 weeks of age, the animals were euthanized and their proximal femurs were fixed and decalcified. Samples were sectioned and analyzed by histology to define extracellular matrix (ECM) structure, immunohistochemistry (IHC) to identify types II and X collagen, and histomorphometry to assess articular cartilage mean total and localized height and cell density. Statistics included nested mixed-effects ANOVA with p ≤ 0.05 considered statistically significant.

RESULTS

Compared to controls, hypothyroid articular cartilage demonstrated statistically significant quantitative differences in mean tissue height, mean cell density and type II collagen localized zone height. Qualitative differences in ECM proteoglycans and overall collagen types were also found. Type X collagen was not detected in either hypothyroid or control articular cartilage specimens.

CONCLUSIONS

Significant changes in articular cartilage structure in hypothyroid compared to control immature miniature swine suggest that thyroid hormone is critical in the growth and development of articular cartilage.

CLINICAL SIGNIFICANCE

Understanding articular cartilage development in immature animal models may provide insight into healing or repair of degenerative human articular cartilage.

Bernoulli-Assisted Percutaneous Removal of an Intra-articular Foreign Body: A Case Report

CASE

A 4-year-old child presented with an intra-articular broken sewing needle in her knee. It was removed arthroscopically using a spinal needle percutaneously placed posterior to the tibia in line with the long axis of the sewing needle. The stylet was partially withdrawn to allow the sewing needle to lay within the spinal needle hollow. When the stylet was removed, the foreign body was propelled through the spinal needle by the increased velocity of the outflowing fluid and decreased pressure (Bernoulli's principle) and was caught in a specimen container.

CONCLUSION

This percutaneous technique is one of several for removing a small foreign body.

Onabotulinum toxin type A injection into the triceps unmasks elbow flexion in infant brachial plexus birth palsy: A retrospective observational cohort study

Brachial plexus birth palsy (BPBP) is a neurologic injury that can result in mild to full paralysis of the affected upper extremity. In severe cases, nerve surgery is often performed before age 1 year. Several studies report gains in elbow flexion with onabotulinum toxin type A (OBTT-A) injections to the triceps; however, its use in infants is not widely reported. The purpose of this study is to present our experience using these injections before 6 months of age to therapeutically unmask elbow flexion and diagnostically guide surgical decision making.This is a retrospective observational cohort study. The cohort included infants with BPBP who received OBTT-A injection to the triceps before age 6 months. Indications for the injections include trace elbow flexion and palpable co-contraction of the biceps and triceps. Elbow flexion was evaluated using the Toronto Test score. Therapeutic success was defined as an increase in post-injection scores. These scores were then used diagnostically as an indication for surgery if the infant did not achieve full elbow flexion by 8 months. A treatment algorithm for OBTT-A triceps injection was developed based on all treatment options offered to infants with elbow flexion deficits seen in the clinic.Of the 12 infants that received OBTT-A triceps injections, 10 (83%) had improved Toronto test elbow flexion scores post-injection. Gains in elbow flexion once attained were maintained. Of the 9 OBTT-A infants with at least 2 years follow-up, 4 achieved full elbow flexion without surgery; the remainder after surgery. No complications with OBTT-A injections were noted and patients were followed on average 6 years. The average age at time of injection was 4 months (range: 2-5 months). Compared to other treatments given, OBTT-A infants tended to present with more elbow flexion than the 4 infants requiring immediate surgical intervention and less elbow flexion than the 16 infants treated conservatively.OBTT-A injection to the triceps in infants with BPBP before 6 months of age therapeutically improved elbow flexion and diagnostically guided surgical decisions when full elbow flexion was not achieved by 8 months of age with no known complications.

Results through skeletal maturity of planned fibular nonunion for the treatment of genu varum in achondroplasia: An observational retrospective study

Current surgical options for treating genu varum in achondroplasia include tibial and fibular osteotomy and growth modulation using plates and screws. However, a single surgeon consistently treated genu varum using a planned fibular nonunion (PFN). The purpose of this study is to describe his surgical technique and report radiographic and clinical outcomes for the cohort studied.This is an observational retrospective review. The cohort studied included patients with achondroplasia who had PFN surgery for the treatment of genu varum at a young age (<13 years) and was followed through to skeletal maturity. The surgery included meticulous closure of the periosteum over the remaining fibula. The surgery was considered a success if the patient did not require subsequent surgery and had acceptable or improved clinical alignment. Radiographic measures used to determine change in genu varum included the anatomic tibio-femoral angle (aTFA), tibia varus, and tibia-fibula ratio. Clinically, changes in lower limb alignment were defined using a plumb line and 6 categories of alignment ranging from extreme varus to valgus. Statistics were used to validate the plumb line categorization to available radiographic measures. Other appropriate statistical methods were used with P < .05 considered significant.Of the 53 PFN cases (27 patients) included in the study, 34 (64%) did not require subsequent surgery and had acceptable or improved alignment. The average age at surgery and follow-up was 6.1 and 17.0 years, respectively. For the 37 limbs (19 patients) with available radiographs, pre- and post-surgery radiographic measures significantly improved including aTFA (3° varus to 2° valgus, P = .003), tibia varus (2° varus to 3° valgus, P = .004), and the tibia-fibula ratio (0.977 to 1.013, P < .001). Clinically, 32 cases (60%) demonstrated significant improvement by translating into an improved alignment and 9 (17%) remained the same (P < .01). Complications were minimal and insignificant. Failures were readily managed by tibia-fibular osteotomies in adolescence and at maturity.PFN for the treatment of genu varum in young achondroplasia patients significantly improved radiographic and clinical measures of lower limb alignment through skeletal maturity with relatively few complications.

An investigation to validate the equivalence of physes obtained from different anatomic regions in a single animal species: Implications for choosing experimental controls in clinical studies

Control tissue in studies of various orthopedic pathologies is difficult to obtain and presumably equivalent biopsies from other anatomic sites have been utilized in its place. However, for growth plates, different anatomic regions are subject to dissimilar mechanical forces and produce disproportionate longitudinal growth. The purpose of this study was to compare gene expression and structure in normal physes from different anatomic regions within a single animal species to determine whether such physes were equivalent. Thirteen female New Zealand white rabbits (five 15-week-old and eight 19-week-old animals) were euthanized and physes harvested from their proximal and distal femurs and proximal tibiae. Harvested physes were divided into groups for histological, immunohistochemical (IHC), and reverse transcription-quantitative polymerase chain reaction analyses. All physes analyzed demonstrated no apparent differences in morphology or proteoglycan staining intensity on histological examination or in type II collagen presence determined by IHC study. Histomorphometric measures of physeal height as well as gene expression of type II collagen and aggrecan were found to be statistically significantly equivalent (p < 0.05) among the three different bones from the total number of rabbits. Summary data suggest that the structural similarities and statistical equivalence determined among the various physes investigated in the rabbit validate these tissues in this species for use as surrogate controls by which physeal abnormalities may be compared and characterized in the absence of otherwise normal control tissues. Other species may exhibit the same similarities and equivalence among different physes so that such tissues may serve in like manner as controls for assessing a variety of orthopedic conditions, including those occurring in humans.

Dynamic tracking influenced by anatomy following medial patellofemoral ligament reconstruction: Computational simulation

BACKGROUND

Continued patellar instability can occur following medial patellofemoral ligament (MPFL) reconstruction. Computational simulation of function was used to investigate the influence of the lateral position of the tibial tuberosity, trochlear dysplasia and patella alta on lateral patellar tracking following MPFL reconstruction.

METHODS

Multibody dynamic simulation models were developed to represent nine knees being treated for recurrent patellar instability. Knee extension against gravity and dual limb squatting were simulated with and without simulated MPFL reconstruction. Graft resting lengths were set to allow 10mm and five millimeters of patellar lateral translation at 30° of knee flexion. The bisect offset index, lateral tibial tuberosity to posterior cruciate ligament tibial attachment (TT-PCL) distance, lateral trochlear inclination, and Caton-Deschamps index were quantified at every five degrees of knee flexion to characterize lateral tracking, lateral position of the tibial tuberosity, trochlear dysplasia, and patella alta, respectively. For the pre-operative and post-operative conditions and each type of motion, bisect offset index was correlated with the anatomical parameters using stepwise multivariate linear regression.

RESULTS

For both motions, the pre-operative and post-operative bisect offset indices were significantly correlated with lateral trochlear inclination and lateral TT-PCL distance. For both motions, the adjusted r² decreased with MPFL reconstruction, but was still approximately 0.5 for MPFL reconstruction allowing five millimeters of lateral translation.

CONCLUSION

MPFL reconstruction decreases but does not eliminate lateral maltracking related to trochlear dysplasia and a lateralized tibial tuberosity. Patients with these pathologies are likely at the highest risk for instability related to maltracking following MPFL reconstruction.

Microarray analysis of slipped capital femoral epiphysis growth plates

BACKGROUND

Microarray technology has been used to analyze gene expression in patients with and without slipped capital femoral epiphysis (SCFE).

METHODS

Proximal femoral physis core biopsies from two patients with SCFE were compared with two control specimens from age-matched patients without SCFE. Extracted RNA from frozen ground samples was subjected to microarray analysis with data tests for statistical significance between SCFE and control tissues.

RESULTS

Compared to controls, SCFE samples demonstrated significant up-regulation in gene expression pathways involving physiological defense and inflammatory responses and significant down-regulation in the regulation of cellular physiologic processes, cellular metabolic pathways, and skeletal development pathways including expression of aggrecan and type II collagen, genes affecting physeal structure and integrity.

CONCLUSIONS

Up-regulation of inflammatory and immune response pathways in SCFE compared to controls relates to physeal mechanical displacement in SCFE. Globalized down-regulation of several other pathways suggests growth plate weakening. These novel microarray findings further define SCFE etiology.

Fibular Allograft and Demineralized Bone Matrix for the Treatment of Slipped Capital Femoral Epiphysis

Previous studies documented the use of fibular allograft in the treatment of slipped capital femoral epiphysis (SCFE) with bone graft epiphysiodesis (BGE). This study describes the results of using a 10-mm diameter premilled fibular allograft packed with demineralized bone matrix placed across the physis in an open surgical approach under image intensification. A review identified 45 cases of BGE using fibular allograft and demineralized bone matrix in 34 patients with a diagnosis of SCFE performed by a single surgeon during an 8-year period. Thirty-four cases (25 patients) had at least 1 year of follow-up and were included in the study. Medical records were reviewed for complications, subsequent surgeries, and time to physeal closure. Of the 34 cases included, there were no cases of acute chondrolysis. Complications included 1 case of bone graft extrusion that required surgical replacement and 1 re-slip requiring surgical stabilization. Five cases of avascular necrosis (AVN) were encountered (1 unstable slip with total head AVN, and 4 stable slips with 3 total head and 1 partial head AVN). In 1 patient, small loose bony fragments were noted on postoperative radiographs that appeared outside of the articular surface of the hip and were asymptomatic. Two patients encountered wound healing issues that resolved with appropriate wound care. In light of the occurrence of AVN in stable cases, BGE with autogenous corticocancellous graft is preferable to BGE with autologous fibular graft for the treatment of SCFE. [Orthopedics. 2016; 39(3):e519-e525.].

Partial or non-union after triple arthrodesis in children: does it really matter?

PURPOSE

Triple arthrodesis is a commonly performed salvage procedure to correct hindfoot deformity. Non-union is considered an undesirable radiographic outcome; however, the clinical ramifications of this are not as well defined. The purpose of this study was to determine the incidence of partial or complete radiographic non-union after triple arthrodesis in children and characterize the clinical consequences.

METHODS

An IRB-approved retrospective review of triple arthrodesis surgeries in patients less than 16 years of age performed by a single surgeon (DSW) identified 159 cases meeting the inclusion criteria. Plain radiographs were reviewed for bony fusion (defined as over 80 % radiographic bony union of the subtalar, calcaneocuboid, and talonavicular bones) and charts for clinical outcomes (pain, return to activity, and subsequent hindfoot surgeries). Statistics were used to compare the fused and unfused cases, with p < 0.05 considered to be significant.

RESULTS

Of the 159 cases included in the study, 9 % did not achieve at least 80 % plain film radiographic union. The fused and unfused groups had similar clinical outcomes. Only one patient required surgery for sequelae of symptoms arising from a pseudoarthrosis related to the triple arthrodesis. The fused and unfused groups were similar in terms of gender and pin removal time, but differed significantly in surgical age and underlying diagnosis.

CONCLUSIONS

This is one of the largest case series of pediatric triple arthrodesis surgery presented in the literature. This study demonstrated that good clinical outcomes can be achieved despite the lack of radiographic union after triple arthrodesis surgery in children.

LEVEL OF EVIDENCE

IV.

Evaluation of Limited Screw Density Pedicle Screw Constructs in Posterior Fusions for Adolescent Idiopathic Scoliosis

STUDY DESIGN

Retrospective case series.

OBJECTIVES

To compare radiographic and clinical outcomes in posterior spine fusions with pedicle screw instrumentation of varying screw densities in the treatment of adolescent idiopathic scoliosis (AIS).

SUMMARY OF BACKGROUND DATA

Posterior spinal fusion with pedicle screw instrumentation is the mainstay of surgical treatment for AIS. The most commonly used construct consists of screws placed at every level on the concave side of the deformity and nearly every level on the convex side. However, some surgeons have begun using constructs with fewer pedicle screws. The literature comparing outcomes of these differing pedicle screw constructs is limited.

METHODS

Fifty-two consecutive cases of posterior spinal fusions for AIS performed by four surgeons were reviewed. High screw density constructs were used in 26 cases and limited screw density constructs in 26 cases. Construct characteristics and radiographic measurements were compared preoperatively and at last follow-up. Operative time and estimated costs were also evaluated. Student t tests were used to compare the groups with p < .05 considered significant.

RESULTS

There was no significant difference in magnitude of correction for the high versus limited screw density group initially (38.5° vs. 34.9°, p = .093) or at final follow-up (36.9° vs. 32.2°, p = .054). Sagittal alignment, coronal balance, and translation of the major apical vertebra were comparable and stable in both groups. The high versus limited screw density group utilized significantly more pedicle screws (16.8 vs. 11.6 screws, p < .0001), had longer operative times (309 vs. 267 minutes, p = .007), and had additional estimated direct costs of $5,800.

CONCLUSIONS

Excellent curve correction, stability, and balance can be achieved using fewer screws than commonly used in posterior pedicle screw fusions for AIS. Operative time is reduced, and risk and cost are decreased with the use of limited screw density constructs.

LEVEL OF EVIDENCE

III.

Gene expression differences between ruptured anterior cruciate ligaments in young male and female subjects

BACKGROUND

The incidence of anterior cruciate ligament (ACL) injuries is two to eightfold greater in female compared with male athletes. Anatomic, hormonal, and neuromuscular factors have been associated with this disparity. This study compared gene expression and structural features in ruptured but otherwise normal ACL tissue from young female and male athletes.

METHODS

A biopsy sample of ruptured ACL tissue (which would normally have been discarded) was obtained intraoperatively from seven female and seven male athletes (12.7 to 22.6 years old). Each sample was divided into portions for histological and gene expression analyses. Specimens for gene analysis were frozen and ground, and RNA was extracted and purified. Microarray analysis was performed on RNA isolated from four female and three male study participants (13.9 to 18.5 years old) who had a noncontact injury. Genes with an expression level that differed significantly between these female and male athletes were grouped into functionally associated networks with use of IPA software (Qiagen). Three genes of interest were chosen for further validation by RT-qPCR (reverse transcription-quantitative polymerase chain reaction) analysis of the samples from all fourteen patients. Several statistical methods were used to examine sex-related differences.

RESULTS

Microarray analysis of the RNA isolated from the ruptured ACL tissue from the female and male athletes identified thirty-two genes with significant differential expression. Fourteen of these genes were not linked to the X or Y chromosome. IPA analysis grouped these genes into pathways involving development and function of skeletal muscle and growth, maintenance, and proliferation of cells. RT-qPCR confirmed significant differences in expression of three selected genes: ACAN (aggrecan) and FMOD (fibromodulin) were upregulated in female compared with male study participants, and WISP2 (WNT1 inducible signaling pathway protein 2) was downregulated. No morphological differences among the ruptured tissue from the various participants were apparent on histological examination.

CONCLUSIONS

The genes identified in this study as differing distinctly according to sex produce major molecules in the ACL extracellular matrix. Significant upregulation of ACAN and FMOD (which regulate the matrix) and downregulation of WISP2 (which is involved in collagen turnover and production) may account for the weaker ACLs in female compared with male individuals.

Anatomical factors influencing patellar tracking in the unstable patellofemoral joint

PURPOSE

The current study was performed to relate anatomical parameters to in vivo patellar tracking for pediatric patients with recurrent patellar instability.

METHODS

Seven pediatric patients with recurrent patellar instability that failed conservative treatment were evaluated using computational reconstruction of in vivo patellofemoral function. Computational models were created from high-resolution MRI scans of the unloaded knee and lower-resolution scans during isometric knee extension at multiple flexion angles. Shape matching techniques were applied to replace the low-resolution models of the loaded knee with the high-resolution models. Patellar tracking was characterized by the bisect offset index (lateral shift) and lateral tilt. Anatomical parameters were characterized by the inclination of the lateral ridge of the trochlear groove, the tibial tuberosity-trochlear groove distance, the Insall-Salvati index and the Caton-Deschamps index. Stepwise multivariable linear regression analysis was used to relate patellar tracking to the anatomical parameters.

RESULTS

The bisect offset index and lateral tilt were significantly correlated with the lateral trochlear inclination (p≤0.002) and TT-TG distance (p<0.05), but not the Insall-Salvati index or the Caton-Deschamps index. For both the bisect offset index and lateral tilt, the standardized beta coefficient, used to identify the best anatomical predictors of tracking, was larger for the lateral trochlear inclination than the TT-TG distance.

CONCLUSION

For this population, the strongest predictor of lateral maltracking that could lead to patellar instability was lateral trochlear inclination.

LEVEL OF EVIDENCE

Diagnostic study, Level II.

An operative approach to address severe genu valgum deformity in the Ellis-van Creveld syndrome

BACKGROUND

The genu valgum deformity seen in the Ellis-van Creveld syndrome is one of the most severe angular deformities seen in any orthopaedic condition. It is likely a combination of a primary genetic-based dysplasia of the lateral portion of the tibial plateau combined with severe soft-tissue contractures that tether the tibia into valgus deformations. Progressive weight-bearing induces changes, accumulating with growth, acting on the initially distorted and valgus-angulated proximal tibia, worsening the deformity with skeletal maturation. The purpose of this study is to present a relatively large case series of a very rare condition that describes a surgical technique to correct the severe valgus deformity in the Ellis-van Creveld syndrome by combining extensive soft-tissue release with bony realignment.

METHODS

A retrospective review examined 23 limbs in 13 patients with Ellis-van Creveld syndrome that were surgically corrected by two different surgeons from 1982 to 2011. Seven additional patients were identified, but excluded due to insufficient chart or radiographic data. A successful correction was defined as 10° or less of genu valgum at the time of surgical correction. Although not an outcomes study, maintenance of 20° or less of genu valgum was considered desirable. Average age at surgery was 14.7 years (range 7-25 years). Clinical follow-up is still ongoing, but averages 5.0 years (range 2 months to 18 years). Charts and radiographs were reviewed for complications, radiographic alignment, and surgical technique. The surgical procedure was customized to each patient's deformity, consisting of the following steps: 1. Complete proximal to distal surgical decompression of the peroneal nerve 2. Radical release and mobilization of the severe quadriceps contracture and iliotibial band contracture 3. Distal lateral hamstring lengthening/tenotomy and lateral collateral ligament release 4. Proximal and distal realignment of the subluxed/dislocated patella, medial and lateral retinacular release, vastus medialis advancement, patellar chondroplasty, medial patellofemoral ligament plication, and distal patellar realignment by Roux-Goldthwait technique or patellar tendon transfer with tibial tubercle relocation 5. Proximal tibial varus osteotomy with partial fibulectomy and anterior compartment release 6. Occasionally, distal femoral osteotomy

RESULTS

In all cases, the combination of radical soft-tissue release, patellar realignment and bony osteotomy resulted in 10° or less of genu valgum at the time of surgical correction. Complications of surgery included three patients (five limbs) with knee stiffness that was successfully manipulated, one peroneal nerve palsy, one wound slough and hematoma requiring a skin graft, and one pseudoarthrosis requiring removal of hardware and repeat fixation. At last follow-up, radiographic correction of no more than 20° of genu valgum was maintained in all but four patients (four limbs). Two patients (three limbs) had or currently require revision surgery due to recurrence of the deformity.

CONCLUSION

The operative approach presented in this study has resulted in correction of the severe genu valgum deformity in Ellis-van Creveld syndrome to 10° or less of genu valgum at the time of surgery. Although not an outcomes study, a correction of no more than 20° genu valgum has been maintained in many of the cases included in the study. Further clinical follow-up is still warranted.

LEVEL OF EVIDENCE

IV.

The effects of hypothyroidism on the proximal femoral physis in miniature swine

As a potential means of comparing hypothyroidism in humans, this work intended to establish a defined hypothyroid state in immature miniature swine and evaluate specific molecular, cellular, and extracellular responses of their growth plates. Two male, 11-week-old Sinclair miniature swine were given 6-propyl-2-thiouracil (PTU) in their water and two other like animals (controls) were provided water without PTU. Blood levels of thyroid stimulating hormone (TSH), triiodothyronine (T3), and thyroxin (T4) were monitored weekly. At 25 weeks of age, the hind limb proximal femoral physes were harvested and divided into portions for histology and reverse transcription-quantitative polymerase chain reaction (RT-qPCR) analysis. Compared to controls, swine administered PTU exhibited increased TSH and decreased T3 and T4 serum levels during the study period, features consistent with a hypothyroid state. Compared to controls, hypothyroid swine exhibited structurally altered physes and demonstrated significantly decreased gene expression of aggrecan (p < 0.05) and type X collagen (p ≤ 0.1). This is the first hypothyroid model established in miniature swine and represents a potentially important advance for understanding the condition in humans, in which, like this swine model, there are changes critical to growth plate molecular biology, biochemistry and structure.

Limited benefit of hamstrings forces for the anterior cruciate ligament-deficient knee: an in vitro study

The hamstrings are considered stabilizers of the anterior cruciate ligament-deficient knee; however, anterior cruciate ligament injury primarily influences tibiofemoral kinematics near full extension, where the hamstrings have the least influence on kinematics. Ten knees were tested at multiple flexion angles in vitro to directly compare the influence of anterior cruciate ligament injury and hamstrings activation on tibiofemoral kinematics. Tibiofemoral kinematics were measured for three testing conditions: (1) anterior cruciate ligament intact, with forces applied through the quadriceps muscles (596 N), (2) anterior cruciate ligament cut, with forces applied through the quadriceps, and (3) anterior cruciate ligament cut, with forces applied through the quadriceps and hamstrings (200 N). Based on repeated measures comparisons performed at each flexion angle, cutting the anterior cruciate ligament significantly (p < 0.05) increased tibial anterior translation, medial translation, and internal rotation at 0 degrees and 15 degrees of flexion by approximately 2.5 mm, 1 mm, and 2 degrees, respectively. Internal rotation also increased significantly at 30 degrees. With the anterior cruciate ligament cut, loading the hamstrings significantly decreased anterior translation, medial translation, and internal rotation at 45 degrees, by approximately 2 mm, 2 mm, and 4 degrees, respectively. Loading the hamstrings caused kinematic changes in the opposite direction of the anterior cruciate ligament injury, but the changes occurred at deeper flexion angles than those at which anterior cruciate ligament injury influenced tibiofemoral kinematics.

A study in vivo of the effects of a static compressive load on the proximal tibial physis in rabbits

BACKGROUND

The effect of compression on the physis is generally defined by the Hueter-Volkmann principle, in which decreased linear growth of the physis results from increased compression. This investigation examined whether mechanically induced compression of rabbit physes causes changes in gene expression, cells, and extracellular components that promote physeal resilience and strength (type-II collagen and aggrecan) and cartilage hypertrophy (type-X collagen and matrix metalloprotease-13).

METHODS

Static compressive loads (10 N or 30 N) were applied for two or six weeks across one hind limb proximal tibial physis of thirteen-week-old female New Zealand White rabbits (n = 18). The contralateral hind limb in all rabbits underwent sham surgery with no load to serve as an internal control. Harvested physes were divided into portions for histological, immunohistochemical, and quantitative reverse transcription-polymerase chain reaction analysis. Gene expression was statistically analyzed by means of comparisons between loaded samples and unloaded shams with use of analysis of variance and a Tukey post hoc test.

RESULTS

Compared with unloaded shams, physes loaded at 10 N or 30 N for two weeks and at 10 N for six weeks showed histological changes in cells and matrices. Physes loaded at 30 N for six weeks were decreased in thickness and had structurally disorganized chondrocyte columns, a decreased extracellular matrix, and less intense type-II and X collagen immunohistochemical staining. Quantitative reverse transcription-polymerase chain reaction analysis of loaded samples compared with unloaded shams yielded a significantly (p ≤ 0.05) decreased gene expression of aggrecan and type-II and X collagen and no significant (p > 0.05) changes in the matrix metalloprotease-13 gene expression with increasing load.

CONCLUSIONS

Compressed rabbit physes generate biochemical changes in collagens, proteoglycan, and cellular and tissue matrix architecture. Changes potentially weaken overall physeal strength, consistent with the Hueter-Volkmann principle, and lend understanding of the causes of pathological conditions of the physis.

The use of the reconstruction plate in multiplanar tibial osteotomies in children

PURPOSE

External fixation and cross-pin fixation appear to be the two most commonly used forms of fixation after a tibial osteotomy in children described in the literature. The purpose of this study is to describe our experience using a properly bent and contoured reconstruction plate for mismatched surfaces after a multiplanar tibial osteotomy.

METHODS

A retrospective review was conducted of 37 multiplanar tibial osteotomy surgeries in 23 children performed by a single surgeon using a reconstruction plate for internal fixation. A low fibular osteotomy and tibial osteotomy that required contouring and shaping of the plate were performed in all cases. A proximal tibial osteotomy was performed in 30 cases and a distal osteotomy in seven cases. All cases were reinforced with a long-leg cast. All charts were reviewed for intra- and postoperative complications. The surgery using the reconstruction plate internal fixation was considered to be a success if there was healing of the osteotomy and no hardware failure.

RESULTS

A properly bent and contoured reconstruction plate conformed well to the mismatched surfaces after tibial osteotomy. Hardware was removed in all but two cases, on average 7 months after surgery. There were no hardware failures. No child developed a deep wound infection or neurovascular complication, including compartment syndrome. Only two complications in 37 surgeries (5%) were encountered and were typical of any type of internal fixation. One child required an exploratory procedure because of screw extrusion and one child developed a post-plate removal fracture.

CONCLUSIONS

The reconstruction plate is very malleable and can be contoured to fit in nearly every direction to accommodate mismatched appositional surfaces. It has been successfully employed in 37 consecutive cases of multiplanar tibial osteotomy in children with relatively few complications, none directly related to the plate.

Multiplanar supramalleolar osteotomy in the management of complex rigid foot deformities in children

PURPOSE

Residual midfoot and hindfoot deformities in rigidly deformed feet present a very complicated surgical dilemma. A plantigrade foot is desirous for proper lower extremity mechanics in a child with ambulatory potential. In this group of patients, soft tissue procedures are no longer an appropriate option, and well-recognized hindfoot procedures, such as talectomy, have many disadvantages. This study reviews the results obtained using multiplanar supramalleolar osteotomy as a salvage procedure to correct deformities of the complex rigid foot in children.

METHODS

A retrospective review was conducted of 27 multiplanar supramalleolar osteotomies in 18 children. The underlying diagnosis of the patients included seven severely rigid idiopathic clubfeet, five arthrogryposis, two myelodysplasia, one Ellis-van Creveld, one Streeter's, one cerebral palsy, and one severe burn contracture. The average age at surgery was 5.6 years, and follow-up averaged 8 years. A successful outcome was deemed a plantigrade foot on physical exam with follow-up of at least 2 years and no subsequent tibial surgeries. All failures were included regardless of the length of follow-up.

RESULTS

A plantigrade attitude of the hindfoot was obtainable at the time of surgery in all cases. Eighteen of the 27 feet had a successful outcome. Nine of 27 (33%) feet had recurrence of the foot deformity requiring additional surgery. Time to recurrence averaged 5.7 years (9 months-13 years). Complications from the surgery included four minor wound healing problems, two delayed unions, and one screw recession, all of which healed without consequences. There was no evidence of nonunion, growth plate closure, infection, or fracture above or through screw holes.

CONCLUSION

The multiplanar supramalleolar osteotomy appears to be a reasonable salvage procedure for severely scarred and complex rigid foot deformities and can be reinstituted for failures due to remaining growth.

Fracture incidence following plate removal in Legg-Calvé-Perthes disease: a 32-year study

PURPOSE

The decision of whether or not to remove pediatric metallic implants remains a controversial issue. Many factors have been cited both in favor and against routine removal of metallic implants. The purpose of this study was to determine the fracture rate following the routine removal of hardware from patients with Legg-Calvé-Perthes (LCP) disease treated by proximal femoral varus osteotomy (PFVO) and to determine if there is an optimal time to remove hardware in this population.

METHODS

We performed a retrospective chart review of children who had PFVO with subsequent hardware removal from March 1973 to May 2005 performed by a single surgeon. A total of 196 hips in 184 patients were included. Data was analyzed using logistic regression. Inverse prediction was also used to obtain estimates of the time needed to produce probabilities of no fracture.

RESULTS

Ten out of the 196 hips included (5.1%) sustained a fracture after plate removal. The time from osteotomy to plate removal averaged 10.4 months in the nonfracture group and 4.8 months in the fracture group. This was statistically significant (P < 0.0001). Using the logistic regression model, the predicted time to plate removal corresponding to a 95% probability of no fracture was between 5.1 and 8.4 months.

CONCLUSIONS

Plate removal remains a reasonable choice but questions remain as to the timing of removal. These data suggest that patients may benefit from extending the time to hardware removal beyond radiographic union to at least six months or more after the osteotomy.