Bone lengthening in rabbits by callus distraction. The role of periosteum and endosteum

Experimental study of progressive tibial lengthening in dogs using the Ilizarov technique. Comparison with and without associated intramedullary K-wires

A delay in the union of bone regenerate in surgical lengthening procedures and the healing index (HI) are major factors in the quality of the results in progressive bone lengthening. Early removal of the external fixator (EF) is associated with a low rate of postoperative complications, including pin track infection, and with better muscle and joint function recovery. Addition of intramedullary wires (IMWs) to the EF led to a 9-49% decrease in the HI depending on the clinical series. We hypothesized that IMWs may accelerate the ossification process of bone regenerate and tested it in this experimental study.

METHODS

Progressive tibial lengthening of 28 mm was obtained in 12 dogs operated with the classical Ilizarov technique (group I) and in 12 dogs operated with the same technique and addition of two IMWs 1.5 mm in diameter (group II). The following criteria were assessed: HI, X-ray measurements, and histological aspect of the bone regenerate and postoperative complications.

RESULTS

The mean HI was 32.3% lower in group II than in group I. The radiological bone union criteria were observed on day 15 of the fixation period in group II versus day 30 in group I. Histology showed that maturation occurred earlier and bone cortices were thicker in group II than group I. Intramedullary ossification was present along the IMW in group II, whereas it was absent in group I. No clinical complications were observed in either group.

DISCUSSION

The presence of the IMWs clearly contributes to stimulation of the ossification processes of the bone regenerate and to acceleration of bone union. IMWs allowed an earlier removal of the external fixator for a 32% time reduction compared to cases without IMWs. In addition, new intramedullary bone formation and presence of IMWs are expected to increase the mechanical resistance of the bone regenerate.

CONCLUSION

Improvement of quantitative and qualitative criteria of bone regenerate in progressive bone lengthening with an EF combined with IMWs was demonstrated in this experimental study.

SIGNIFICANCE

Favorable results encourage the authors to continue using IMWs in addition to the EF in patients treated with long-bone progressive lengthening.

LEVEL OF EVIDENCE

II.

Bony periosteum-covered iliac crest plug transplantation for severe osteochondral lesions of the talus: a modified mosaicplasty procedure

PURPOSE

This study reports first evidence of a modified procedure for osteochondral autologous transplantation where bony periosteum-covered plugs are harvested at the iliac crest and transplanted into the talar osteochondral lesion.

METHODS

Thirteen out of 14 patients, average age 39.6 (SD 14.4) years, were followed clinically and radiographically for a median of 25 (24-28) months (minimal follow-up, 24 months).

RESULTS

For these 13 patients, the American Orthopaedic Foot and Ankle Society hindfoot score increased from 47 (SD 11) points pre-operatively, to 81 (SD 14) points postoperatively (p < 0.0001). The average pain score decreased from 6.6 (SD 1.3) points pre-operatively, to 1.4 (SD 1.9) points postoperatively (p < 0.0001). Seven patients returned to sports activity. Radiographically good plug osteointegration was observed in nine out of 11 ankles. Follow-up arthroscopy showed fibrous cartilage in four ankles, periosteum hypertrophy in five ankles, and partial or total missing of coverage of the bone in three ankles. Three revision surgeries had to be performed.

CONCLUSIONS

This modified mosaicplasty might be recommended for severe and recurrent osteochondral lesions of the talus and may lead to restoration of the subchondral bone stock, formation of fibro-cartilage, and stable joint function.

LEVEL OF EVIDENCE

IV.

Experimental assessment of a novel intramedullary nail for callus distraction by the segmental bone transport method

BACKGROUND

Segmental bone transport (SBT) is a revolutionary method for treating extensive bone defects, and it is in wide clinical use. Although external fixation is generally used to perform SBT, it is associated with problems such as complications due to pin placement and limitations of the amount and rate of lengthening. As a way to overcome these problems we developed a novel intramedullary (IM) nail for SBT that minimizes damage to the surrounding tissue and improves the amount and rate of bone lengthening. The purpose of this study was to perform SBT in the femur of beagle dogs using the novel IM nail that we devised, and to evaluate the morphology and quality of the regenerated bone and circulation status in the surrounding tissue. We also considered the possibilities and limitations of the IM in regard to clinical application.

METHODS

This experiment was conducted on six beagle dogs. The novel IM nail we devised was inserted into the marrow cavity of the femur, and a 30-mm bone defect was created. After a 7-day postoperative waiting period, a bone segment was transported by 1.0 mm per day in two 0.5-mm increments. Because the nail broke in two dogs, they received only partial elongation by 15 mm over a 15-day period, with a 15-mm defect remaining, whereas full elongation by 30 mm in 30 days was performed in the other four dogs. The elongation was followed by a 30-day bone hardening period.

RESULTS

The macroscopic and histological results demonstrated that high-quality, new bone had replaced the 30-mm bone defect created in the femur of all six dogs. The density and number of blood vessels that had penetrated the elongated segment of bone from the surrounding muscles was greater than in the corresponding segment of the contralateral femur, which served as a control. The results imply that the traction stimulus induced vigorous angiogenesis in the surrounding tissue.

CONCLUSION

We concluded that this method has tremendous potential for clinical application, and will overcome the limitations of conventional external fixators.

Effects of caffeic acid phenethyl ester and melatonin on distraction osteogenesis: an experimental study

Aim

The aim of this experimental animal model study is to investigate the effects of caffeic acid phenethyl ester (CAPE) and melatonin on the maturation of newly-formed regenerated bone in distraction osteogenesis.

Methods

Unilateral femoral lengthening(extension) was applied to 39 adult male Wistar albino rats, which were randomly allocated to 3 groups of 13; control, melatonin and CAPE groups. Through a 7-day latent waiting period and 15 days of distraction, melatonin of 25 mg/kg and CAPE of 10 μmol/kg were administered to the respective groups. The animals were sacrificed on Day 82. Radiographic, histological and biomechanical evaluations were made and measurements were taken.

Results

At the end of 82 days, the distraction osteogenesis area was seen to be completely filled with new bone formation in all 3 groups both radiologically and histologically. Biomechanically, the maximum torsional fracture strength (Maximum Torque (N-m)) of the melatonin group was higher compared to that of the control group, although it was not statistically significant (p > 0.05). The maximum torsional momentum of the CAPE group was statistically significantly high (p < 0.05). The degree of rigidity (N-m/deg) of both the melatonin and CAPE groups was higher than that of the control group and the CAPE group was found to be statistically significantly higher than the melatonin group (p < 0.05).

Conclusion

Melatonin and CAPE increase the maturation of new bone in distraction osteogenesis. These effects are probably due to the reducing effect on bone resorption by inhibiting NF-κB and free oxygen radicals.

Hinged circular fixator construct for correction of congenital metatarsal deformity in a foal

A five-week-old American Quarter Horse colt was presented for evaluation of a left hindlimb deformity and lameness. Radiographs of the left hindlimb revealed a varus deformity with recurvatum originating in the mid-diaphysis of the third metatarsal bone. Surgical correction was undertaken by performing an osteotomy through the centre of rotation of angulation located within the mid-diaphysis of the third metatarsal bone, and a four-ring hinged circular external fixator construct was applied. Distraction of the osteotomy site was performed over an 11 day period. Notable complications included failure of a fixation pin, infection of the surgical site, and temporary laxity of the supporting tendons and ligaments of the contralateral metatarsophalangeal joint. The fixator was maintained until there was sufficient bone formation to allow frame removal, 152 days after the initial surgery. Use of a hinged circular construct allowed for partial correction of the deformity with resultant lengthening and resolution of the lameness in this colt.

Prophylactic titanium elastic nailing (TEN) following femoral lengthening (Lengthening then rodding) with one or two nails reduces the risk for secondary interventions after regenerate fractures: a cohort study in monolateral vs. bilateral lengthening procedures

BACKGROUND

Femoral fracture rates of up to 30% have been reported following lengthening procedures using fixators. "Lengthening then rodding" uses one or two titanium elastic nails (TENs) for prophylactic intramedullary nailing to reduce this complication. The aim of the study was to decide if usage of only one TEN is safe or has it a higher risk of getting a fracture? And we asked if there is a difference between patients with monolateral or bilateral lengthening procedures according to their fracture rate?

METHODS

One or two TENs were implanted in two groups of patients (monolateral and bilateral) after femoral lengthening procedures. The regenerate quality was classified using the Li system and fractures were categorized using the Simpson and Kenwright classification. The follow-up period was at least 1 year after removal of the frame.

RESULTS

Sixty-seven patients with 101 femoral lengthening procedures were included in 2007-2011. Group A included 34 patients with bilateral lengthening due to congenital short stature. Group B consisted of 33 patients with congenital disorders with leg length discrepancies. Seven fractures in six patients were seen in group A and five fractures in group B. One patient had residual shortening of 1 cm, and 11 fractures healed without relevant deviation (< 5°) or shortening (< 5 mm). A soft-tissue infection in one patient led to early removal of one TEN.

CONCLUSIONS

Fractures occurred in both groups of patients in total in 12 of the 101 cases (12%). The rate of secondary interventions was markedly reduced. Usage of one or two TENs did not influence the fracture rate.

Periosteal cells are a major source of soft callus in bone fracture

During the healing process after bone fracture, soft callus forms adjacent to the fracture site, is replaced by hard callus, and is finally remodeled to the original bone configuration. Although the cambium layer of the periosteum is reported to play an essential role in callus formation, we still lack direct in vivo evidence of this. To investigate the cell lineage of the soft callus, we analyzed the process of fracture healing in Prx1-Cre;ROSA26 reporter (R26R), Col1a1(3.6 kb)-Cre;R26R, Col1a1(2.3 kb)-Cre;R26R, Sox9-CreERT2;R26R, and Sox9-LacZ mice with X-gal staining. In the Prx1-Cre;R26R, in which the cells of the periosteum stained for X-gal before fracture, all cells in the soft callus were X-gal positive, whereas in the Col1a1(3.6 kb)-Cre;R26R mice, the cells in the periosteum before fracture stained for X-gal and the soft callus was partly composed of X-gal-positive cells. In contrast, in the Col1a1(2.3 kb)-Cre;R26R mice, in which the mature osteoblasts in the cambium layer of the periosteum were marked before fracture, no cells in the soft callus at the fracture site were X-gal positive. These results suggest that most of the cells in the soft callus are derived from the mesenchymal progenitors in the periosteum, and not from mature osteoblastic cells. Interestingly, in the Sox9-LacZ mice, Sox9-expressing X-gal-positive cells emerged in the periosteum adjacent to the fracture site 3 days after fracture. We demonstrated this by injecting tamoxifen into the Sox9-CreERT2;R26R mice for 3 days after fracture, so that these Sox9-expressing periosteal cells gave rise to cells in the soft and hard calli. Our findings show that the periosteal cells in which Sox9 expression is induced just after fracture are the major source of the chondrocytes and osteoblasts in the fracture callus.

Vector-controlled alveolar distraction osteogenesis using an implant-fixed provisional prosthesis: a case report

This is a case report of anterosuperior alveolar distraction using an implant-fixed provisional prosthesis. Osteotomy and placement of a distraction device were performed in a healthy 69-year-old woman. To avoid lingual inclination during the distraction period, the device's rod was buried in the labial side of a provisional prosthesis supported by posterior implants. The mandibular bone was obliquely distracted by 0.3 mm every 2 days. Implant insertion was performed, and a good prognosis was anticipated. Inclination is thought to be caused by soft tissue on the lingual side. Many reports propose methods to avoid inclination, but these methods require established support from the teeth and cannot be adapted for an edentulous case. The method reported here is useful for distraction osteogenesis because it can be adapted for edentulous cases.

Complications of Albizzia femoral lengthening nail: an analysis of 36 cases

Thirty-six cases of femoral lengthening using the Albizzia nail were performed. The indication for lengthening was a congenital malformation, sequellae of trauma, of infection, of radiation therapy, short stature, and vascular malformation. The mean age of the patients was 16 years, the average lengthening achieved was 4.7 cm, and the follow-up period averaged 5.8 years. We found that bone consolidation was achieved faster than with external fixation. The patient's comfort during lengthening as well as the speed of functional restoration also improved. In three cases, the program failed, in six the lengthening was achieved with a second procedure, and eight patients required one ratcheting or more under general anesthesia. In our experience, the Albizzia nail is a simple and effective solution for uncomplicated femoral lengthening.

Current concepts of leg lengthening

Any lower limb discrepancy may be equalised by conservative means (insoles, prosthesis and orthosis). However, their long-term acceptance is low in regard to function, costs, expenditure and appearance. Timely epiphysiodesis is the best option in uniplanar deformities with adequate remaining growth and for patients whose predicted final body height is above the 50th percentile. However, many patients present late or with multi-planar deformities, which warrant more sophisticated operative approaches. The history of surgical bone lengthening comprises 100 exciting years of struggling, development and ongoing learning. The initial strategy of acute or rapid incremental distraction had lasted almost half a century until Ilizarov recognised the benefits of biological periosteum-preserving osteotomies and incremental lengthening at slow rates (1 mm/day) at a 4 × 0.25-mm daily rhythm, well appreciated as callotasis. In parallel, ring and wire constructs made complex three-dimensional axial, translational and rotational bone moulding possible. Taylor Spatial Frames-built on hexapod strut-linked platform technology as known from flight simulators-took limb correction to a more reliable, more precise and aesthetical level, all the more that the whole process became web-based. It represents state-of-the-art methodology and technology for complex, multi-plane deformities. Due to the significant risk of secondary malalignment, indications for lengthening by unilateral fixation have shrunken to moderate amounts of length disparity and uni- to bi-planar deformities in patients with still open physes. Mechanical or motorised, minimally invasively placed nails prevent muscle fixation and, therefore, ease rehabilitation, increase patient comfort and potentially shorten the overall time of sick leave and refrain from sports activities. Hence, they offer a valuable alternative for low-grade complexity situations. It remains to be proved if the significantly higher implant costs are compensated by lower treatment costs. Overall, limb lengthening, particularly in combination with multi-planar deformity correction, can still be an arduous endeavour. In any case, wise judgement of the patient's deformity, medical and biological situation, psychosocial environment, selection of the appropriate method and hardware, as well as meticulous operating technique by an experienced surgeon are the cornerstones of successful outcomes.

Relative contributions of osteogenic tissues to new bone formation in periosteal distraction osteogenesis: histological and histomorphometrical evaluation in a rat calvaria

BACKGROUND

The relative contributions of different, potential factors to new bone formation in periosteal distraction osteogenesis are unknown.

PURPOSE

The aim of the present study was to assess the influence of original bone and periosteum on bone formation during periosteal distraction osteogenesis in a rat calvarial model by means of histology and histomorphometry.

METHODS

A total of 48 rats were used for the experiment. The contribution of the periosteum was assessed by either intact or incised periosteum or an occlusive versus a perforated distraction plate. The cortical bone was either left intact or perforated. Animals were divided in eight experimental groups considering the three possible treatment modalities. All animals were subjected to a 7-day latency period, a 10-day distraction period and a 7-day consolidation period. The newly formed bone was analyzed histologically and histomorphometrically.

RESULTS

New, mainly woven bone was found in all groups. Differences in the maximum height of new bone were observed and depended on location. Under the distraction plate, statistically significant differences in maximum bone height were found between the group with perforations in both cortical bone and distraction plate and the group without such perforations.

CONCLUSIONS

If the marrow cavities were not opened, the contribution to new bone formation was dominant from the periosteum. If the bone perforations opened the marrow cavities, a significant contribution to new bone formation originated from the native bone.

Callus patterns in femoral lengthening over an intramedullary nail

Our objectives were to evaluate callus patterns seen in femoral lengthening over an intramedullary nail by Li classification regarding shape and type and to predict the result while using the nail to reduce the external fixation period and its complications. Eight hundred digital radiographs of 15 patients with 15 segments of femur shortening who underwent femoral lengthening with a monolateral external fixator over an intramedullary nail were analyzed retrospectively by four observers. Each radiograph was studied for callus shape, feature type, and callus density using pixel values. The classification was tested for concurrence and reproducibility by interobserver studies and callus patterns were compared with treatment indices to evaluate how they correlated with the outcome. Mean length gained was 4.5 cm (range: 2-8 cm). External fixator index (EFI) was 21.68 days/cm. Average distraction consolidation index (DCI) was 48.49 days/cm. Fusiform callus was seen in three cases, cylindrical in seven, and lateral in five. The homogenous pathway had higher DCI (43.7) than the heterogeneous pathway (32.9), and mixed pathways making up the rest had a DCI of 50.1. Pixel value of callus showed gradual increase in density until 20-24 weeks, then density gradually fell for 8 weeks, again increased after 32 weeks, again gradually fell, and was comparable to adjacent normal bone by 44-48 weeks. Our results suggest that the Li classification can be satisfactorily applied to lengthening procedures over intramedullary nails. The radiologic pattern and pixel value of regenerate can be correlated with the clinical outcome and can be an aid of prognostic value for the surgeon.

Bone regeneration and limb lengthening

Regeneration of bone in the presence of stable fixation and the maintenance of the osteogenic tissue (marrow, endosteum, nutrient artery, and periosteum) required another factor to stimulation of bone regeneration: incremental distraction produces bone of both endosteal and periosteal origin. The soft tissues undergo to same growth phenomenon. The mechanism of ossification occurs without intermediate fibrocartilage.

Distraction osteogenesis for bone repair in the 21st century: lessons learned

Bone regeneration obtained by distraction osteogenesis is influenced by a series of factors. These include factors that are related to the mechanical stability of the system of distraction (internal or external devices), and to factors directly depending on the biology of the bone tissue, such as the method of bone interruption (osteotomy), the delay and rhythm of distraction, the anatomical site of the osteotomy, and the histological characteristics of the bone requiring reconstruction. The stability of the system of bone fixation depends on the rigidity of the frame, the connexion of the apparatus to the bone (wires, pins) and the intrinsic stability of the segment (length and level of maturation of bone regenerate). The radiological characteristics of bone regeneration (hypo- or hypertrophy) lead to the adaptation of the rhythm of distraction. Following more than 28 years of experience of application of the Ilizarov method for bone reconstruction, the authors describe the technique of frame assembly and the methods of evaluation and treatment of the complications of new bone formation.

Bone lengthening (distraction osteogenesis): a literature review

Distraction osteogenesis (DO) is a surgical technique widely used in orthopedic surgery for the treatment of various pathological conditions such as leg length discrepancy, bone deformity or bone defects. The basic principle of the callotasis technique includes performing a transverse bone section before gradually distracting the two bone segments. New bone tissue is generated in the gap between the two segments. Bone regeneration during DO is believed to occur in response to the longitudinal mechanical strain applied to the callus during healing. One of the limitations of this technique is the long period of time required for the newly formed bone tissue to mineralize and consolidate. Various studies have reported that among growth factors, bone morphogenetic proteins (BMPs) may play a central role in the molecular signaling cascade leading to bone renegeration and remodeling in a DO procedure. Ongoing research is aimed at developing methods to accelerate bone consolidation in order to reduce the time required to obtain consolidation. One of these methods is to test the ability of exogenous BMPs to increase bone regeneration and accelerate bone consolidation.

Macroscopic and microscopic process of long bone fracture healing

The growth of each type of callus (cortical, medullary and periosteal) depends on the mechanical condition of fracture fixation (elastic fixation and instability or rigid immobilization), the type of treatment (non-operative, close or open surgical procedure, intra-medullary nailing, external fixation, plate...) and the high or poor quality of soft tissue and the specific characteristics of the local vascularisation.

Transcription factor osterix modified bone marrow mesenchymal stem cells enhance callus formation during distraction osteogenesis

This study was designed to investigate the effects of local delivery of bone marrow mesenchymal stem cells (BMMSCs) with or without osterix (OSX) gene transfected on bone regeneration in the distracted zone using a rabbit model of mandibular lengthening. Fifty-four New Zealand white rabbits underwent osteodistraction of the left mandible and were then randomly divided into group A, group B, and group C (n = 18 for each group). At the end of distraction BMMSCs transfected with OSX, autologous BMMSCs and physiological saline were injected into the distraction gaps in groups A, B, and C, respectively. Nine animals from each group were humanely killed at 2 and 6 weeks after completion of distraction. The distracted mandibles were harvested and processed for radiographic, histological, and immunohistochemical examination. Excellent bone formation in the distracted callus was observed in group A and group B; the former showed better bone formation and highest bone mineral density (BMD), thickness of new trabeculae (TNT, mm) and volumes of the newly formed bone area (NBV) in the distraction zones. Group C animals showed poor bone formation in the distracted callus when compared with groups A and B. Positive immunostaining of bone sialoprotein (BSP) was observed in the distracted callus in all groups; however, BSP expression was much stronger in group A than in groups B and C. The results of this study suggest transplantation of BMMSCs can promote bone formation in DO; OSX-mediated ex vivo gene therapy was more effective during bone deposition and callus formation in distraction osteogenesis.

Use of an interlocking nail-hybrid fixator construct for distal femoral deformity correction in three dogs

Our purpose was to report the use of an interlocking nail-hybrid external fixator construct to correct distal femoral deformities in three dogs. Radiographs, computed tomography and a three-dimensional model were used to plan the surgical procedure. A femoral osteotomy or ostectomy was performed at the level of the centre of rotation of angulation in all three dogs. Angular and rotational deformities were corrected acutely. Distraction osteogenesis was performed to lengthen each femur postoperatively. All three dogs had additional anatomic abnormalities of the affected hindlimb complicating the correction of the distal femoral deformity. While the interlocking nail-hybrid fixator construct allowed for stable distraction of the femur, all three dogs developed complications during the postoperative convalescent period, and each had some degree of residual lameness. Lengthening the femur following acute deformity correction is problematic and additional experimental and clinical studies are warranted to decrease postoperative morbidity and improve functional results.

An interspecies computational study on limb lengthening

Distraction osteogenesis is a surgical technique that produces large volumes of new bone by gradually separating two osteotomized bone segments. A previously proposed mechanical-based model that includes the effect of pre-traction stresses (stress level in the gap tissue before each distraction step) during limb lengthening is used here. In the present work, the spatial and temporal patterns of tissue distribution during distraction osteogenesis in different species (sheep, rabbit) and in the human are compared numerically to predict experimental results. Interspecies differential characteristics such as size, distraction protocol, and rate of distraction, among others, are chosen according to experiments. Tissue distributions and reaction forces are then analysed as indicators of the healing pattern. The results obtained are in agreement with experimental findings regarding both tissue distribution and reaction forces. The ability of the model to qualitatively predict the two animal models and the human healing pattern in distraction osteogenesis indicates its potential in understanding the influence of mechanics in this complex process.

Insufficient bone regenerate after intramedullary femoral lengthening: risk factors and classification system

BACKGROUND

Control of distraction rate with an intramedullary skeletal kinetic distractor (ISKD) may be problematic and a high distraction rate may result in insufficient bone regenerate.

QUESTIONS/PURPOSES

Are distraction problems preventable when using the ISKD, and what are the risk factors for and radiologic types of insufficient bone regenerate during ISKD lengthening?

PATIENTS AND METHODS

We analyzed 37 consecutive ISKD femoral lengthening procedures in 35 patients with a mean age 33 ± 11 years and minimum followup of 12 months (average, 27 ± 9 months; range, 12-55 months). The average length gain was 42.8 ± 12.9 mm.

RESULTS

Eight patients had problems during distraction: seven had "runaway nails" and one had a nondistracting nail. Insufficient bone regenerate developed in eight patients. Important risk factors were a distraction rate greater than 1.5 mm/day (9.1 times higher risk), age 30 years or older, smoking, and lengthening greater than 4 cm. Less important risk factors identified were creation of the osteotomy at the site of previous trauma or surgery and acute correction of associated deformities. We proposed a radiologic classification for failure of bone regeneration: partial regenerate failure (Type I) or complete failure resulting in a segmental defect subdivided according to a length of 3 cm or less (Type IIa) or greater than 3 cm (Type IIb).

CONCLUSIONS

Distraction problems with the ISKD were related mostly to internal malfunction of the lengthening mechanism. A distraction rate greater than 1.5 mm/day should be avoided in femoral intramedullary lengthening. Smoking should be a contraindication for femoral lengthening.

LEVEL OF EVIDENCE

Level II, prognostic study. See Guidelines for Authors for a complete description of levels of evidence.

Callus features of regenerate fracture cases in femoral lengthening in achondroplasia

OBJECTIVE

We studied the callus features seen in cases of regenerate fracture in femoral lengthening using a monolateral fixator in achondroplasia to determine whether callus types and shapes can predict the probability of callus fracture.

MATERIALS AND METHODS

The radiographs of 28 cases of femoral lengthening in 14 patients, 14 cases of callus fracture, and 14 cases without callus fracture were retrospectively analyzed by four observers and classified into different shapes and types in concordance with the Ru Li classification.

RESULTS

The average lengthening of 9.4 cm (range 7.5-11.8 cm) was achieved, which was 41% (range 30-55%) of the original length and the average timing of callus fracture was 470 days (range 440-545 days) after surgery in the callus fracture group. While the average lengthening of 9.1 cm (range 8-9.7 cm) was achieved, this was 30% (range 28-32%) of the original length in the group of patients without callus fracture. The callus was atypically shaped, there was a 48% average (range 30-72%) reduction of the callus width compared with the natural width of the femur, and a lucent pathway was present in all cases of regenerate fracture.

CONCLUSION

A lucent pathway was seen in all fracture cases with concave, lateral, and atypical shapes, and there was more than 30% lengthening and 30% reduction of the callus width compared with the natural width of the femur, which are the warning signs for regenerate fractures. These signs help the surgeon to predict the outcome and guide him in planning for any additional interventions. The Ru Li classification is an effective method for the evaluation of the chance of callus fracture.

Segmental fracture of the femur with concomitant genu valgum: a one-stage solution

Segmental fractures of the femur are high energy injuries usually treated with internal fixation. We present the case of such a fracture in which the femur had a preexisting genu valgum deformity from an earlier distal femur physeal arrest. This prevented standard intramedullary nailing or minimally invasive plate fixation. A technique of simultaneous correction of the distal femoral deformity coupled with stabilization of the segmental fracture is reported. Surgery involved an external fixator-assisted corrective osteotomy of the deformity and simultaneous minimally invasive plating of the segmental fracture. The advent of modern concepts of deformity correction has allowed a combination with present day internal fixation techniques to achieve correction, stabilization and union in a problem that would otherwise require two stages of surgery.

The non-vascularised fibular graft: a simple and successful method of reconstruction of the pelvic ring after internal hemipelvectomy

Internal hemipelvectomy is a standard treatment for malignant tumours of the pelvis. Reconstruction using a non-vascularised fibular graft is relatively straightforward compared to other techniques. We describe the surgical and functional outcomes for a series of ten patients who underwent an internal hemipelvectomy (type I or I/IV) with reconstruction by a non-vascularised fibular graft between 1996 and 2009. A key prerequisite for this procedure was a preserved sciatic notch, confirmed pre-operatively on MRI. Graft-host union was achieved in all patients with a single fibular graft, and in the lower graft where two grafts had been used. The mean time to union was 7.3 months (3 to 12). The upper graft did not unite in four of six cases where two grafts had been used. Seven patients were eventually able to walk without a stick. The mean post-operative Musculoskeletal Tumour Society score was 75.4% (16.7 to 96.7). There were no cases of deep post-operative infection. The mean pelvic shortening was 0.9 cm (0.2 to 3.4). Recurrent tumour occurred in three cases, and death from tumour-related disease occured in one. Patients who need an internal hemipelvectomy will do well if their pelvic ring is reconstructed with a non-vascularised fibular graft. The complication rate is low, and they attain a good functional outcome.

Bone lengthening osteogenesis, a combination of intramembranous and endochondral ossification: an experimental study in sheep

We evaluated the morphological features of the newly formed tissue in an experimental model of tibial callotasis lengthening on 24 lambs, aged from 2 to 3 months at the time of operation. A unilateral external fixator prototype Monotube Triax^® (Stryker Howmedica Osteonics, New Jersey) was applied to the left tibia. A percutaneous osteotomy was performed in a minimally traumatic manner using a chisel. Lengthening was started 7 days after surgery and was continued to 30 mm. The 24 animals were randomly divided into three groups of 8 animals each: in Group 1, lengthening took place at a rate of 1 mm/day for 30 days; in Group 2, at a rate of 2 mm/day for 15 days; in Group 3, at a rate of 3 mm/day for 10 days. In each group, 4 animals were killed 2 weeks after end of lengthening, and the other 4 animals at 4 weeks after end of lengthening. To assess bony formation in the distraction area, radiographs were taken every 2 weeks from the day of surgery. To study the process of vascularization, we used Spalteholz’s technique. After killing, the tibia of each animal was harvested, and sections were stained with hematoxylin and eosin, Masson’s trichrome, and Safranin-O. Immunohistochemistry was performed, using specific antibodies to detect collagens I and II, S100 protein, and fibronectin. A combination of intramembranous and endochondral ossification occurred together at the site of distraction. Our study provides a detailed structural characterization of the newly formed tissue in an experimental model of tibial lengthening in sheep and may be useful for further investigations on callotasis.

Objective guidelines for removing an external fixator after tibial lengthening using pixel value ratio: a pilot study

During limb lengthening over an intramedullary nail, decisions regarding external fixator removal and weightbearing depend on the amount of callus seen at the lengthening area on radiographs. However, this method is subjective and objective evaluation of the amount of callus likely would minimize nail or interlocking screw breakage and refracture after fixator removal. We asked how many cortices with full corticalization of the newly formed bone at the lengthening area are needed to allow fixator removal and full weightbearing and how to radiographically determine the stage of corticalization. We retrospectively reviewed 17 patients (34 lengthenings) who underwent bilateral tibial lengthenings over an intramedullary nail. The average gain in length was 7.2 +/- 3.4 cm. We determined the pixel value ratio (ratio of pixel value of regenerate versus the mean pixel value of adjacent bone) of the lengthened area on radiographs. There were no nail or screw breakage and refracture. Partial weightbearing with crutches was permitted when the pixel value ratio was 1 in two cortices and full weightbearing without crutches was permitted when the pixel value ratio was 1 in three cortices. The pixel value ratio on radiographs can be an objective parameter for callus measurement and may provide guidelines for the timing of external fixator removal. We cannot determine from our limited data the minimum pixel value in how many cortices would suggest safe removal, but we can say our criteria were not associated with subsequent refracture.

Bilateral sagittal split osteotomies and mandibular distraction osteogenesis: a randomized controlled trial comparing skeletal stability

OBJECTIVE

To conduct a randomized controlled trial comparing the skeletal stability of bilateral sagittal split osteotomy (BSSO) and mandibular distraction ostoegenesis (MDO) for moderate mandibular advancement.

STUDY DESIGN

Fourteen class II mandibular hypoplasia patients requiring mandibular advancement between 6 and 10 mm were randomized into 2 groups for either BSSO or MDO. Serial lateral cephalographs were taken 2 weeks, 6 weeks, 12 weeks, 6 months, and 12 months after surgery for the assessment of skeletal stability. The Student t test was used to analyze stability with statistical significance set at P < .05.

RESULTS

There was no significant difference (P > .05) in horizontal and vertical skeletal relapse between the 2 groups at every postoperative time period.

CONCLUSIONS

Although the MDO group reported less horizontal and vertical skeletal relapse for mandibular advancements between 6 and 10 mm at 1 year, no statistically significance was found between the groups. Other patient-related factors need to be considered when choosing one technique over the other.

Experimental study of bone lengthening in dogs by means of backscattered scanning electron microscopy

OBJECTIVE

To describe the morphology of calcified tissues involved in distraction osteogenesis (DO) by means of backscattered scanning electron microscopy (BS-SEM).

STUDY DESIGN

Experimental study.

ANIMALS

Adult female Beagle dogs (n=12).

METHODS

Non-simultaneous and bilateral transverse mid-diaphyseal osteotomies performed in tibiae were stabilized and distracted by a Type Ia external skeletal fixation device. After a latency period of 5 days, distraction was applied at a rate of 0.5 mm every 12 hours for 10 days. Then, the external fixator was maintained in a static mode during the consolidation period until bone healing or euthanasia at 1, 2, 3, 4, 6, 8, 10, 12, 14, and 18 weeks after operations, whichever came first. Distracted regions were isolated and their structure was examined by BS-SEM.

RESULTS

Calcified chondroid tissue was prominent during distraction and calcified cartilaginous tissue during consolidation; both tissues were successively replaced by woven, lamellar, and osteonal bone.

CONCLUSIONS

In osteotomized tibia, chondroid tissue is the main component of the mineralization front during distraction, calcified cartilaginous tissue during consolidation, and then both tissues are replaced by woven, lamellar, and osteonal bone. The ossification mechanism of distraction callus is transchondroidal.

CLINICAL RELEVANCE

BS-SEM is an effective technique for studying progression of bone healing during DO. The presence of chondroid tissue during DO explains why callus mineralization occurs more rapidly during distraction than during static stabilization.

Quantitative screening of engineered implants in a long bone defect model in rabbits

We have standardized a long bone defect model in rabbits to quantitatively compare the bone healing performance of engineered biological implants and have tested the bone healing efficiency of porous cylindrical scaffolds (ø-h, 6-20 mm [diameter 6 mm, height 20 mm] porosity, 70%) that were produced from hydroxyapatite (HA), titanium (Ti), and a novel biodegradable polymer-bioceramic composite (PH70alphaTCP). Scaffolds were perfused with or without 20 x 10(6) rabbit periosteal cells (RPCs) in a bioreactor and implanted in a standardized 2 cm defect in rabbit tibiae. X-rays revealed that new bone had formed at 3 weeks after creation of the defects. At sacrifice after 10 weeks, bone corticalization was observed in the majority of animals. Although PH70alphaTCP scaffolds did not inhibit callus formation, histomorphometric analysis revealed that there was no bone within the biomaterial, in contrast to HA and Ti scaffolds (bone volume ranging from 10% to 25%). We found that Ti and HA scaffold had good osteoconductive properties, but only HA scaffolds seeded with RPCs contributed to long bone mechanical functionality, with the maximum energy and angle being 308% and 155% greater than in control defects without scaffold.

Measurement of bone electrical impedance in fracture healing

BACKGROUND

Although external fixation is widely used for fractures and limb lengthening, evaluation of the time for removing the external fixator is dependent upon radiographic examinations and clinical findings, and a useful method has yet to be established clinically. This study aimed to measure the bone electrical impedance (Z values) non-invasively by using external fixation pins as electrodes, and clarify the relationship with bone union.

METHODS

Thirty rabbits received the external fixation at the right tibia and were assigned to a control group (group C; n = 5) and a fractured group (group F; n = 25). Z values were measured once a week following surgery. The animals of group F were assigned to 5 groups (weeks 2, 3, 4, 5, and 6 after osteotomy, each n = 5). The resistivity (rho) of the electrical property between electrodes was measured prior to euthanasia, and fracture cross-sectional area (FrA) of the conduction pathway and maximum bending stress (Bmax) were measured following excision of the tibia.

RESULTS

Although Z values in group F increased through 5 weeks after surgery, Z values in group C remained constant at 3 weeks, and significant differences were observed between groups at 4, 5, and 6 weeks. The rho values and FrA in group F decreased through 5 weeks; while Bmax increased, reaching a plateau at 5 weeks.

CONCLUSIONS

Narrowing of conduction pathway due to the decrease in the contour of fracture area accompanying bone remodeling resulted in an increase of Z values. Both Z values and Bmax in group F reached a peak at 5 weeks, this was believed to be the optimal time for removal of external fixation. These results suggest that measurement of Z values makes it possible to evaluate bone union.

Optimal increase in bone mass by continuous local infusion of alendronate during distraction osteogenesis in rabbits

Several methods have been used to increase bone mass in distraction osteogenesis. Since bone resorption as well as regeneration is stimulated in the distracted segment, bisphosphonate can be a beneficial agent for distraction osteogenesis. Here, we examined the effects of bisphosphonate injected continuously into the regenerate on bone volume, and architectural and mechanical properties of distraction osteogenesis. The left tibia of Japanese White rabbits (n=66) was subjected to slow distraction using an external fixator. At the beginning of the consolidation phase, alendronate (7 microg/kg/day) was infused directly into the lengthened segment for 14 days using an osmotic pump. Control rabbits were infused with phosphate buffered saline (PBS). The tibiae were monitored weekly by soft X-ray and dual-energy X-ray absorptiometry (DXA). The animals were sacrificed at 4, 6, and 8 weeks after operation to examine bone mineral density (BMD) and cortical bone thickness (CBT) by peripheral quantitative computerized tomography (pQCT), while the mechanical property of the lengthened tibia was measured by three-point bending test. In PBS-infused control animals, bone mineral content around the lengthened segment began to decrease after the first week of consolidation phase, forming a tubular bone structure with thin cortex. Infusion of alendronate increased peak bone mineral content around the lengthened segment. At the end of the experiment, volumetric BMD, CBT and mechanical strength of the lengthened segment of the treatment group were approximately twice those of the control animals. Alendronate infused in this manner significantly prevented the osteopenia that critically began early in the consolidation phase, though the dose used in this study was relatively low and no adverse events were noted.

Histology of the regenerate and docking site in bone transport

INTRODUCTION

Bone transport is based on the principle of distraction osteogenesis described by Ilizarov and is a consecrated method for the treatment of segmental bone defects. One of its most problematic and, paradoxically, least studied aspects is the consolidation of the docking site. We studied histologically the ossification of the docking site and regenerate to determine any difference between them.

MATERIALS AND METHODS

Nine adult sheep were submitted to correction of a 1-cm tibial diaphyseal defect using a system of plate-fixed bone transport, with latency period of 1 week and 0.2 mm distraction of the transported segment four times a day. The sheep were divided into three groups of three animals each, according to the observation period of 3, 6 or 12 weeks between the fixation of the transported fragment and the euthanasia. The docking site and the regenerate were studied histologically on sections stained with Masson trichrome.

RESULTS

The main mode of docking site ossification was the endochondral one and although intramembranous ossification was also observed simultaneously, it was limited to rare and small foci. In contrast, intramembranous ossification played the major role in the regenerate, with bone formation evolving from the base segment to the target segment.

CONCLUSION

The experimental bone transport model proposed in the present study permits us to conclude that there is a clear difference between the ossification of the docking site and of the regenerate.

Histologic study of the cellular events during rat mandibular distraction osteogenesis

OBJECTIVE

The cellular events, underlying bone regeneration through rat mandibular distraction osteogenesis (DO) was examined using micro computerized tomography (microCT), histology, and histochemistry.

STUDY DESIGN

After 5-day latency, mandibles were distracted at 0.2 mm/12 h for 10 days, and fixed at latency 5 days (L5D), distraction 3, 6, 10 days (D3D, D6D, D10D), and consolidation 1, 3, 6, 10 weeks (C1W, C3W, C6W, C10W).

RESULTS

The microCT demonstrated radiopacity at the distraction gap (DG) during C1W, which was filled with new bone at C6W and C10W. At D3D, collagen fibers were aligned along the axis of the distraction vector. At D6D, alkaline phosphatase-positive osteoblasts and intramembranous ossification was observed. Collagen bundles became thicker with new bony trabeculae at D10D. Type II collagen-immunopositive areas first appeared at C1W. At C3W, cartilage tissue and endochondral ossification were found. By C6W, the entire DG had been bridged by new bone. The C10W specimens showed mature lamellar bone.

CONCLUSION

Mandibular DO produces bone through both intramembranous and endochondral ossification.

Distraction osteogenesis of the femur using conventional monolateral external fixator

INTRODUCTION

The author has developed a new simple technique of distraction osteogenesis using conventional monolateral external fixator for femoral lengthening. The primary purpose of the present study was to evaluate the results of treatment with this new technique of femoral lengthening and also to evaluate the effect of preoperative and intraoperative variables on the outcome of distraction osteogenesis in general.

MATERIALS AND METHODS

Fifty-one femora in 50 patients were lengthened. Limb-length discrepancy was the primary indication in all patients. The mean age of the patients at the time of the surgery was 21.9 years (range 5-48 years). The average follow-up period was 24.6 months after removal of the fixator (range 6-120 months). All lengthenings were performed using conventional AO/ASIF external fixator. Twenty-two femora had associated axial or rotational deformities. Gradual distraction was performed to increase length and to correct angular deformity in coronal plane. Acute closed wedge angular correction in sagittal plane or derotation was performed in 12 femora in this study.

RESULTS

The length of the 51 femora was increased by an average 4.4 cm (range 1-13 cm), or 12% (range 2.5-40.9%). The average healing index was 50.5 days/cm (range 22.5-110.6 days/cm). Average gradual angular correction in coronal plane in 14 femora was 20.4 degrees (range 10-45 degrees ). Average acute correction in sagittal plane in five femora was 17 degrees (range 10-20 degrees ). Average acute derotation in six femora was 24.2 degrees (range 10-60 degrees ). There were a total of 61 complications, including 26 problems, 18 obstacles, and 17 sequelae. The overall rate of complications was 1.2 per femur. Fifteen femora had delayed consolidation (healing index >54 days/cm). Three of 51 lengthening procedures did not lead to consolidation (nonunion). A significant negative parabolic relationship was noted between the healing index and the amount of length gained (R = -0.47 and P = 0.004). There was a significantly positive exponential relationship between age and healing index (R = 0.51 and P < 0.001). Acute deformity correction, level of osteotomy (submetaphysis versus diaphysis) had no significant effect on healing index. The greater amount of length gained was associated with complications.

CONCLUSIONS

The newly presented technique of distraction osteogenesis is a useful and cost-effective method for femoral lengthening. Increased lengthenings produced a better healing index but might associate with complications. Younger age was associated with better bone healing but age had no effect on complication rate. Level of osteotomy, acute deformity correction had no effect on healing index and rate of complications.