Low-intensity pulsed ultrasound therapy stimulates callus formation between host femur and cortical onlay strut allograft

Cortical onlay strut allografting is a promising surgical option to reconstruct and reinforce the deficient femur in a hip arthroplasty. However, the union of the allograft to the host bone takes a long time. To accelerate the process of cortical onlay strut allograft healing, we studied the effects of low-intensity pulsed ultrasound (LIPUS) on callus formation. From 2 wk after the operation, LIPUS was given for 20 min/d at each end of the strut allograft. The LIPUS treatment group was assigned 14 allograft transplantations, while 21 control patients were treated without LIPUS. The LIPUS treatment group formed calluses and had complete bridging between the host femur and the allograft faster after operation (16.9 and 29.4 wk after operation, respectively) compared with the control group (40.7 and 82.0 wk after operation, respectively). Our findings showed that LIPUS stimulated bone bonding between the host femur and the cortical onlay strut allografts.

[An alternative model of composite tissue transplantation in rat: the femur osteomyocutaneous flap]

OBJECTIVE

To reconstruct a simpler and reliable composite tissue transplantation model-the femur osteomyocutaneous flap for the replacement of hindlimb transplantation.

METHODS

Ten femur osteomyocutaneous flaps from 5 Lewis rats were transplanted into 10 syngeneic recipients' inguinal region. Their nutrient vessels were anastomosed with recipients vessels. The graft of this model was consisted of the groin flap and partial femur. To verify the feasibility of this model, gross and histological appearance were studied after transplantation to evaluate the viability of grafts.

RESULTS

The operative time was (159.0 +/- 8.3) min with the harvesting time of (68.0 +/- 4.8) min and the ischemia time of (55. 8 +/- 6.8) min. The methylene blue injection showed rich blood supply of transplanted femur osteomyocutaneous flap. All the 10 flaps survived completely with pink skin color and hair regrowth. The histologic examination of the flaps also revealed the normal appearance of the viable skin and bone marrow.

CONCLUSIONS

The femur osteomyocutaneous flap is a simple and reliable model for composite tissue transplantation, and its establishment will provide a new tool for the study of composite tissue allografts.

Matching osteochondritis dissecans lesions in identical twin brothers

Osteochondritis dissecans is a disorder of unknown etiology that can result in fragmentation of osteochondral surfaces, most commonly of the knee, shoulder, elbow, and ankle. This may lead to sequelae of pain and an inability to participate in desired activities. Multiple theories exist as to the true cause of the disorder, but none have been fully proven. One such proposed etiology is genetic causation. Familial cases of osteochondritis dissecans are rare, yet these cases offer support to growing evidence that may support a genetic link. This article describes osteochondritis dissecans lesions of the femoral trochlea in monozygotic (identical) twins. Both twins presented with similar symptoms 1 year apart. Neither twin had any clear inciting trauma. Magnetic resonance imaging revealed osteochondral lesions in similar positions of the lateral trochlear of the same knee in both brothers. Osteochondral autograft transfer and tibial tubercle anteromedialization were performed on both patients. An identical postoperative protocol was followed, and recovery with full return to sport was comparable for the brothers. To the authors' knowledge, only 1 other case report exists of osteochondritis dissecans lesions in monozygotic twins. Although debate continues regarding the true etiology of this disorder, cases of identical twins presenting with a similar disease process are highly suggestive of a genetic component and may lead to early identification and treatment of these lesions. Continued research in the area of osteochondritis dissecans and its genetic basis is needed to completely understand this disorder.

Surgical revascularization induces angiogenesis in orthotopic bone allograft

BACKGROUND

Remodeling of structural bone allografts relies on adequate revascularization, which can theoretically be induced by surgical revascularization. We developed a new orthotopic animal model to determine the technical feasibility of axial arteriovenous bundle implantation and resultant angiogenesis.

QUESTIONS/PURPOSES

We asked whether arteriovenous bundles implanted in segmental allografts would increase cortical blood flow and angiogenesis compared to nonrevascularized frozen bone allografts and contralateral femoral controls.

METHODS

We performed segmental femoral allotransplantation orthotopically from 10 Brown Norway rats to 20 Lewis rats. Ten rats each received either bone allograft reconstruction alone (Group I) or allograft combined with an intramedullary saphenous arteriovenous flap (Group II). At 16 weeks, we measured cortical blood flow with the hydrogen washout method. We then quantified angiogenesis using capillary density and micro-CT vessel volume measurements.

RESULTS

All arteriovenous bundles were patent. Group II had higher mean blood flow (0.12 mL/minute/100 g versus 0.05 mL/minute/100 g), mean capillary density (23.6% versus 2.8%), and micro-CT vessel volume (0.37 mm(3) versus 0.07 mm(3)) than Group I. Revascularized allografts had higher capillary density than untreated contralateral femora, while vessel volume did not differ and blood flow was lower.

CONCLUSIONS

Axial surgical revascularization in orthotopic allotransplants can achieve strong angiogenesis and increases cortical bone blood flow.

[Periacetabular pelvic reconstruction for chondrosarcoma with autograft of the proximal femur]

INTRODUCTION

Chondrosarcoma is a malignant tumor of chondroid matrix-producing cells; based on its frequency, it is the second most common malignant bone tumor (10-20%) and responds poorly to chemo- and radiotherapy. It is infrequent in the pelvis. It has a rapid growth potential. The indicated treatment is broad resection with tumor-free margins. Pelvic reconstruction after resection is controversial. The current management of musculoskeletal neoplasias has a two-fold purpose. First of all, controlling the neoplasia by means of surgeries with cancer-free margins and, second, performing procedures for the reconstruction of the involved segment achieving limb preservation with maximum functionality.

OBJECTIVE

Intrapelvic reconstruction with the proximal third of the ipsilateral femur in a patient with a chondrosarcoma in Enneking-Dunham's zone II. And placement of an unconventional femur prosthesis.

CLINICAL CASE

We present herein the case of a 58 year-old male, with a lytic lesion of the right acetabulum. The patient completed the diagnostic protocol, and the biopsy result was dedifferentiated chondrosarcoma.

CONCLUSION

The purpose of the surgical technique is to use the proximal third of the femur as a novel reconstruction alternative with massive autograft for tumor lesions located in Enneking-Dunham zone II.

Vascularized bone grafts for scaphoid nonunions

Scaphoid fractures that fail to unite are at risk of developing avascular necrosis and progressive structural collapse, thereby complicating attempts at revision surgical treatment. Vascularized bone grafts have demonstrated utility in promoting consolidation in the treatment of scaphoid nonunions complicated by avascular necrosis. Numerous pedicled and free vascularized grafts have been described with variable, but generally favorable, outcomes. Understanding the indications for different grafts is critical to the successful application of these techniques and grafts in the treatment of challenging scaphoid nonunions.

Primary tumor of the periacetabular region: resection and reconstruction using a segmental ipsilateral femur autograft

INTRODUCTION

Bone reconstruction, after periacetabular tumour removal, is a complex procedure that carries a high morbidity rate and can result in poor clinical outcomes. Among the available options, the Puget pelvic resection-reconstruction procedure uses an autograft from the ipsilateral proximal femur to restore the anatomical and mechanical continuity of the pelvic ring before inserting an acetabular implant. HYPOTHESIS AND GOALS: This reconstruction technique satisfactorily restores the pelvic anatomy such that functional results and morbidity are comparable to alternative reconstruction techniques.

PATIENTS AND METHODS

This was a retrospective study of 10 patients with an average age of 38.2 years (range 19 to 75) at the surgical procedure (performed between 1986 and 2007). There were five chondrosarcomas, three Ewing tumours, one plasmacytoma and one giant cell tumour. The position of the hip centre of rotation after reconstruction and autograft integration were evaluated on radiographs. Functional results were evaluated through the Musculoskeletal Tumor Society (MSTS) score and the Postel and Merle d'Aubigné (PMA) score.

RESULTS

At the time of review, one patient was lost to follow-up and four had died. On radiographs, the hip centre of rotation after reconstruction was higher by a median value of 15 mm (range 5 to 35) and more lateral by a median value of 6mm (range -5 to 15). Upon evaluation of radiographs at a median time of 40 months (range 6 to 252 months), the autograft was completely integrated in five patients and partially integrated in three patients (two patients had a local recurrence). There were no cases of autograft fracture or non-union at the junctions of the graft. The median MSTS score was 25 out of 30 (range 20 to 29), or 83% (range 67 to 97%) at the median clinical follow-up of 82 months (range 49 to 264). The median PMA score was 13 out of 18 (range 12 to 18). All living patients were walking without assistance. Five patients required nine surgical revisions. Seven were attributed directly or indirectly to local recurrence; one revision was performed because of instability and one because of early acetabular loosening at 9 months.

CONCLUSION

This challenging procedure provides satisfactory mechanical and anatomical results, while restoring hip anatomy and function. The primary cause of failure in this series was local recurrence of the tumour, which highlights the need to carefully select the indications and optimize the surgical tumour resection.

Induced membrane technique for reconstruction after bone tumor resection in children: a preliminary study

AIM

Segmental long-bone defect due to tumor resection remains a challenge to treat. The induced membrane technique is a new alternative for biological reconstruction. During the first stage, a cement spacer is inserted after bone resection and stabilisation. The cement spacer is removed during a second stage procedure performed after chemotherapy, and cortico-cancellous bone autograft was placed in the biological induced chamber. The aim of this study was to assess preliminary results in eight children.

PATIENTS AND METHODS

This prospective study included six girls and two boys, with a mean age of 12.1 years (range 9.5 to 18) and treated for a mean 15 cm defect (range 10 to 22 cms) due to resection of osteosarcoma (n=4), Ewing sarcoma (n=3) and low grade sarcoma. All patients except one, were given pre- and postoperative chemotherapy. Surgery was performed for three patients with a distal femur tumor, two patients with a proximal tibial tumor and three patients who had proximal humerus, shaft of humerus and fibular tumors. Fixation was mainly performed with locking compression plate (n=4) and locked nail (n=2). The mean operating times for first and second step procedures were 4.8 and 4h respectively. The healing process was radiologically assessed.

RESULTS

After a mean follow-up of 21.6 months (15 to 30), all patients were free of disease and seven had bony union. For the lower limb reconstructions, full weight bearing was possible after a mean of 116 days (range 90 to 150) following the second stage. Mean time to bone union was 4.8 months (1.5 to 10). The early Musculoskeletal Tumor Society (MSTS) score was 25.2/30 (range 20-30). Complications were: non-union (n=1), paradoxical graft resorption (n=1) requiring graft revision.

CONCLUSION

This two stage procedure reduces the operating time during the first stage and it also reduces early complications. Rapid bone union is objectively obtained despite major bone resection and the patients receiving chemotherapy.

SIGNIFICANCE

The induced membrane technique could be an excellent alternative for biological reconstruction after tumor resection in children.

Rabbit trochlear model of osteochondral allograft transplantation

Allografting and autografting of osteochondral tissues is a promising strategy to treat articular cartilage lesions in damaged joints. We developed a new model of fresh osteochondral allografting using the entire rabbit trochlea. The objective of the current study was to demonstrate that this model would achieve reproducible graft-host healing and maintain normal articular cartilage histologic, immunolocalization, and biochemical characteristics after transplantation under diverse storage and transplantation conditions. New Zealand white (n = 8) and Dutch belted (n = 8) rabbits underwent a 2-stage transplantation operation using osteochondral grafts that had been stored for 2 or 4 wk. Trochlear grafts harvested from the left knee were transplanted to the right knee as either autografts or allografts. Grafts were fixed with 22-gauge steel wire or 3-0 nylon suture. Rabbits were euthanized for evaluation at 1, 2, 4, 6, and 12 wk after transplantation. All grafts that remained in vivo for at least 4 wk demonstrated 100% interface healing by microCT. Trabecular bridging was present at the host-graft interface starting at 2 wk after transplantation, with no significant difference in cartilage histology between the various groups. The combined histology scores indicated minimal evidence of osteoarthritis. Immunostaining revealed that superficial zone protein was localized at the surface of all transplants. The rabbit trochlear model met our criteria for a successful model in regard to the ease of the procedure, low rate of surgical complications, relatively large articular cartilage surface area, and amount of host-graft bone interface available for analysis.

[Three-dimensional gait analysis of patients with osteonecrosis of femoral head before and after treatments with vascularized greater trochanter bone flap]

OBJECTIVE

To provide the objective basis for the evaluation of the operative results of vascularized greater trochanter bone flap in treating osteonecrosis of the femoral head (ONFH) by three-dimensional gait analysis.

METHODS

Between March 2006 and March 2007, 35 patients with ONFH were treated with vascularized greater trochanter bone flap, and gait analysis was made by using three-dimensional gait analysis system before operation and at 1, 2 years after operation. There were 23 males and 12 females, aged 21-52 years (mean, 35.2 years), including 8 cases of steroid-induced, 7 cases of traumatic, 6 cases of alcoholic, and 14 cases of idiopathic ONFH. The left side was involved in 15 cases, and right side in 20 cases. According to Association Research Circulation Osseous (ARCO) classification, all patients were diagnosed as having femoral-head necrosis at stage III. Preoperative Harris hip functional score (HHS) was 56.2 +/- 5.6. The disease duration was 1.5-18.6 years (mean, 5.2 years).

RESULTS

All incisions healed at stage I without early postoperative complications of deep vein thrombosis and infections of incision. Thirty-five patients were followed up 2-3 years with an average of 2.5 years. At 2 years after operation, the HHS score was 85.8 +/- 4.1, showing significant difference when compared with the preoperative score (t = 23.200, P = 0.000). Before operation, patients showed a hip muscles gait, short gait, reduce pain gait, and the pathological gaits significantly improved at 1 year after operation. At 1 year and 2 years after operation, step frequency, pace, step length and hip flexion, hip extension, knee flexion, ankle flexion were significantly improved (P < 0.01). Acceleration-time curves showed that negative wave and spinous wave at acceleration-stance phase of front feet and hind feet in affected limb were obviously reduced at 1 year and 2 years after operation. Postoperative petronas wave appeared at swing phase; the preoperative situation was three normal phase waves.

CONCLUSION

These results suggest that three-dimensional gait analysis before and after vascularized greater trochanter for ONFH can evaluate precisely hip vitodynamics variation.

Teriparatide therapy enhances devitalized femoral allograft osseointegration and biomechanics in a murine model

Despite the remarkable healing potential of long bone fractures, traumatic injuries that result in critical defects require challenging reconstructive limb sparing surgery. While devitalized allografts are the gold standard for these procedures, they are prone to failure due to their limited osseointegration with the host. Thus, the quest for adjuvants to enhance allograft healing remains a priority for this unmet clinical need. To address this, we investigated the effects of daily systemic injections of 40 μg/kg teriparatide (recombinant human parathyroid hormone) on the healing of devitalized allografts used to reconstruct critical femoral defects (4mm) in C57Bl/6 mice. The femurs were evaluated at 4 and 6 weeks using micro CT, histology, and torsion testing. Our findings demonstrated that teriparatide induced prolonged cartilage formation at the graft-host junction at 4 weeks, which led to enhanced trabeculated bone callus formation and remarkable graft-host integration at 6-weeks. Moreover, we observed a significant 2-fold increase in normalized callus volume (1.04 ± 0.3 vs. 0.54 ± 0.14 mm³/mm; p < 0.005), and Union Ratio (0.28 ± 0.07 vs. 0.13 ± 0.09; p < 0.005), compared to saline treated controls at 6-weeks. Teriparatide treatment significantly increased the torsional rigidity (1175 ± 311 versus 585 ± 408 N.mm²) and yield torque (10.5 ± 4.2 versus 6.8 ± 5.5 N.mm) compared to controls. Interestingly, the Union Ratio correlated significantly with the yield torque and torsional rigidity (R²=0.59 and R²=0.77, p < 0.001, respectively). These results illustrate the remarkable potential of teriparatide as an adjuvant therapy for allograft repair in a mouse model of massive femoral defect reconstruction, and warrant further investigation in a larger animal model at longer time intervals to justify future clinical trials for PTH therapy in limb sparing reconstructive procedures.

Outcomes analysis of anterior-posterior fusion for low grade isthmic spondylolisthesis

BACKGROUND

Traditional surgical treatment of isthmic spondylolisthesis is posterior-lateral fusion, but the addition of anterior surgery has been explored. The purpose of this study was to evaluate the surgical and clinical outcomes of anterior-posterior surgical treatment for low-grade isthmic spondylolisthesis.

METHODS

Retrospectively, we enrolled 23 consecutive patients (mean age of 50) who underwent surgical treatment for low grade isthmic spondylolisthesis. The mean follow-up was 10 months. Basic demographic and radiographic data was collected. Pre- and post-surgical clinical surveys (VAS, ODI, and SF-36) were collected.

RESULTS

All 23 patients underwent anterior interbody fusion with a femoral ring allograft or ICBG in combination with posterior lumbar decompression and fusion with instrumentation. The average slip percentage decreased from 23.2% to 19.0% (p = 0.24) while slip angle increased from 9.8° to 17.9° (p < 0.001) and average disc height decreased from 1.9 cm to 0.80 cm (p < 0.001). VAS scores decreased from 7.1 to 2.4 (p < 0.001), ODI scores decreased from 52.5 to 28.1 (p < 0.001), and SF-36 scores increased in the Physical Component Scale (PCS) from 29.5 to 42.6 (p < 0.001).

CONCLUSION

In our study, patients demonstrated an improvement in the ODI as well the physical component scores of the SF-36, thus having a good clinical outcome.

Biomechanical comparison of translaminar screw versus pedicle screw supplementation of anterior femoral ring allografts in one-level lumbar spine fusion

Pedicle screws (PS) can provide initial stabilization of anterior interbody femoral ring allograft (FRA) lumbar constructs. Translaminar screws (TLS) have also been advocated for this procedure. The objective of this study was to use an in vitro human cadaveric model to compare the stability of one-level anterior interbody lumbar constructs stabilized with PS and those stabilized with TLS. Five human cadaveric spinal motion segments (L4-S2) were biomechanically evaluated in the intact condition and using the follow- ing methods of stabilization: anterior interbody fusion with FRA, anterior FRA supplemented with PS, and anterior FRA supplemented with TLS. Stability was determined for each construct by measuring construct displacement as a function of applied load under the following conditions: compression, flexion, extension, lateral bending to each side, and axial torsion. There were no statistically significant differences in construct stability between FRA supplemented with PS and FRA supplemented with TLS under any of the loading conditions. In selected cases, supplementation of anterior femoral ring allograft with translaminar screws is a viable alternative to supplementation with pedicle screws.

Three-dimensional morphometric analysis of the distal femur: a validity method for allograft selection using a virtual bone bank

Tumor excision is the primary treatment of aggressive or recurrent benign bone tumors and malignant bone sarcomas. This requires a surgical resection with the potential for large residual osseous defects that could be reconstructed using fresh frozen allografts. Virtual bone banks enable the creation of databases allowing a 3D pre-surgery evaluation of such allgorafts, based on segmentation of DICOM-CT images. This study demonstrates the usefulness of patient specific 3D models for an accurate host-donor allograft match. We describe one way to select the best match according to size and shape. The results suggest that a robust and reliable technique has been established. Since it is difficult to plan an allograft on a distal femur deformed by the tumor, we propose to plan the surgery on the contralateral side. Our results support this limb symmetry hypothesis. The use of this measurement protocol enables accurate selection of allografts from a contralateral healthy femur 3D CT model achieving the best match possible considering the geometry of available allograft candidate femur specimens.

[Experimental steroid osteoporosis in rats and the way to restore the bone tissue structure]

Experimental prednisolone administration has been shown to cause osteoporosis in animals. A single administration of fetal tissue--10-day fetal homogeneous tissue at a dose of 0.5 mg into the experimental animal femur improves the bone tissue structure, hastens its remodeling, contributes to elimination of the bone tissue pathologic process in osteoporosis.

Treatment of non-union of forearm bones with a free vascularised corticoperiosteal flap from the medial femoral condyle

We report 6 cases of recalcitrant non-union of forearm bones treated with a free vascularized thin corticoperiosteal graft harvested from the medial condyle of the femur. All non-unions healed. In one 58-year-old patient a fracture of the femur occurred.

[Induction of axial vascularization in processed bovine cancellous bone scaffold using arteriovenous loop]

OBJECTIVE

To explore the method of inducing axial vascularization in a processed bovine cancellous bone scaffold by using an arteriovenous loop, and to evaluate its effect of vascularization.

METHODS

Custom-made processed bovine cancellous bone discs were processed into cylinder with circular grooves. Thirty male SD rats weighing 300-350 g (3-4 months old) were randomly divided into 2 groups (n = 15 per group): experimental group in which the femoral veins in the groin of rats were separated and transplanted to the contralateral femoral artery and vein stump, the processed bovine cancellous bone scaffold was inserted into the arteriovenous loop, which was placed into the annular groove. Control group, in which the blood vessels in the groin of rats were cut, no anastomosis was conducted, and the processed bovine cancellous bone scaffold was planted. At 2, 4 and 8 weeks after operation, gross observation, ink infusion histology observation and microvessel bulk density detection were conducted.

RESULTS

At each postoperative time point, the samples in the experimental group were fresh red, the circulation of blood vessels were smooth bidirectionally, while the samples in the control group were dark red soft, and flexible. Ink infusion histology observation showed the processed bovine cancellous bone scaffold in the experimental group had obvious vascularization, the blood vessels tended to be mature and integrated into network, and neovascular sprouts originated from arteriovenous loop were evident, especially at 8 weeks after operation; while there was no vascularization in the control group. At 2, 4 and 8 weeks after operation, the bulk density of the microvessels in the experimental group was (3.59 +/- 1.84), (16.61 +/- 10.23) and (39.04 +/- 13.46) microm3/microm3, respectively, and it was (2.43 +/- 0.97), (6.79 +/- 2.92) and (25.31 +/- 10.98) microm3/microm3, respectively, in the control group. Significant differences was noted between two groups at 4 and 8 weeks after operation (P < 0.05), and no significant difference was evident at 2 weeks after operation (P > 0.05).

CONCLUSION

Inducing vascularization in a processed bovine cancellous bone using an arteriovenous loop is a new strategy of revascularization and may provide valuable clues for the preparation of functional artificial bone.

Bone graft harvest using a new intramedullary system

Obtaining autogenous bone graft from the iliac crest can entail substantial morbidity. Alternatively, bone graft can be harvested from long bones using an intramedullary (IM) harvesting system. We measured bone graft volume obtained from the IM canals of the femur and tibia and documented the complications of the harvesting technique. Donor site pain and the union rate were compared between the IM and the traditional iliac crest bone graft (ICBG) harvest. Forty-one patients (23 male, 18 female) with an average age of 44.9 years (range, 15-78 years) had graft harvested from long bones using an IM harvest system (femoral donor site, 37 patients; tibial donor site, four patients). Forty patients (23 male, 17 female; average age, 46.4 years; range, 15-77 years) underwent anterior ICBG harvest. We administered patient surveys to both groups to determine pain intensity and frequency. IM group reported lower pain scores than the ICBG group during all postoperative periods. Mean graft volume for the IM harvest group was 40.3 mL (range, 25-75 mL) (graft volume was not obtained for the ICBG group). Using an intramedullary system to harvest autogenous bone graft from the long bones is safe provided a meticulous technique is used.

LEVEL OF EVIDENCE

Level III, retrospective comparative study. See the Guidelines for Authors for a complete description of levels of evidence.

[Voluminous bone graft harvesting of the femoral marrow cavity for autologous transplantation. An indication for the"Reamer-Irrigator-Aspirator-" (RIA-)technique]

Due to their excellent osteoinductive, osteogenetic, and osteoconductive properties, autologous bone grafts possess biomechanical advantages over synthetic bone substitutes. Furthermore, unlike cadaveric allografts and xenografts, they carry no risk of immunogenic response or transmission of infectious diseases. However, the limited availability of autologous bone grafts requires the use of the above-mentioned bone substitutes for management of large bone defects. The"Reamer-Irrigator-Aspirator-" (RIA-)technique may present an alternative method for harvesting a larger volume of autologous bone graft as compared with conventional harvesting procedures. We report on intramedullary reaming by the RIA technique to obtain autologous bone graft for a nonunion of the proximal femur. The contralateral femur was reamed and the bone graft was applied to the nonunion. The patient showed clinical and radiological healing of the nonunion without donor site complications.

Distinct roles for intrinsic osteocyte abnormalities and systemic factors in regulation of FGF23 and bone mineralization in Hyp mice

X-linked hypophosphatemia (XLH) is characterized by hypophosphatemia and impaired mineralization caused by mutations of the PHEX endopeptidase (phosphate-regulating gene with homologies to endopeptidases on the X chromosome), which leads to the overproduction of the phosphaturic fibroblast growth factor 23 (FGF23) in osteocytes. The mechanism whereby PHEX mutations increase FGF23 expression and impair mineralization is uncertain. Either an intrinsic osteocyte abnormality or unidentified PHEX substrates could stimulate FGF23 in XLH. Similarly, impaired mineralization in XLH could result solely from hypophosphatemia or from a concomitant PHEX-dependent intrinsic osteocyte abnormality. To distinguish between these possibilities, we assessed FGF23 expression and mineralization after reciprocal bone cross-transplantations between wild-type (WT) mice and the Hyp mouse model of XLH. We found that increased FGF23 expression in Hyp bone results from a local effect of PHEX deficiency, since FGF23 was increased in Hyp osteocytes before and after explantation into WT mice but was not increased in WT osteocytes after explantation into Hyp mice. WT bone explanted into Hyp mice developed rickets and osteomalacia, but Hyp bone explanted into WT mice displayed persistent osteomalacia and abnormalities in the primary spongiosa, indicating that both phosphate and PHEX independently regulate extracellular matrix mineralization. Unexpectedly, we observed a paradoxical suppression of FGF23 in juvenile Hyp bone explanted into adult Hyp mice, indicating the presence of an age-dependent systemic inhibitor of FGF23. Thus PHEX functions in bone to coordinate bone mineralization and systemic phosphate homeostasis by directly regulating the mineralization process and producing FGF23. In addition, systemic counterregulatory factors that attenuate the upregulation of FGF23 expression in Hyp mouse osteocytes are present in older mice.

Free medial femoral condyle bone grafting for scaphoid nonunions with humpback deformity and proximal pole avascular necrosis

Treatment of scaphoid nonunions remains a challenging problem, especially in the setting of proximal pole avascular necrosis or humpback deformity. Conventional bone grafting techniques have demonstrated unpredictable results in the setting of collapse deformities, whereas pedicled dorsal distal radius vascularized bone grafts have recently been reported to have nearly a 50% failure rate when used in scaphoid nonunions with proximal pole nonunion. Free vascularized medial femoral condyle bone grafting is one option for the treatment of scaphoid nonunions with proximal pole avascular necrosis associated with a humpback deformity. The indications, contraindications, and technique of free vascularized medial femoral condyle bone grafting are presented for the treatment of scaphoid nonunions associated with proximal pole avascular necrosis and humpback deformities.