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Calcaneocuboid distraction arthrodesis (CCDA) is regarded as an effective method for reconstructing adult-acquired flatfoot deformity. In the present study, we present our experience with newly developed rigid β-tricalcium phosphate wedges to treat CCDA to better understand the outcomes of this synthetic bone grafting procedure. A total of 13 feet in 13 patients underwent CCDA with synthetic bone grafts. One male (7.69%) and 12 females (92.31%), with a mean age of 65.07 ± 11.83 (range 36 to 77) years, were followed up for a mean duration of 32.76 ± 12.81 (range 18 to 55) months. Successful graft union was postoperatively obtained in 12 of the 13 feet (92.31%). The mean preoperative visual analog scale and American Orthopaedic Foot and Ankle Society scale score were 7.97 ± 1.52 (range 5.4 to 10) and 54.46 ± 14.72 (range 18 to 75), respectively. These scores improved to 1.52 ± 1.78 (range 0 to 6.2) and 85.46 ± 13.38 (range 50 to 97) postoperatively (p = .001 for both comparisons). On radiographic analysis, the talonavicular coverage angle, first metatarsal talar angle, calcaneal pitch, and heel alignment angle had significantly improved (p = .001, p = .028, p = .006, and p = .001, respectively). The use of bone graft substitutes in CCDA is a viable treatment option for reconstructing flexible flatfoot deformity. Although good clinical and radiographic outcomes were obtained, our method is even more challenging than conventional methods and should be used with caution. Rigid locking fixation with a long period of protected weightbearing is highly recommended to attain uneventful bone healing.
Adult-acquired flatfoot deformity (AAFD), especially when associated with the advanced stage of posterior tibial tendon dysfunction (PTTD), is an extremely challenging, but rewarding, deformity to treat. The treatment options depend on the severity of symptoms and the PTTD stage (
). Generally, conservative treatment has consisted of rest, oral nonsteroidal antiinflammatory drugs, plantar orthosis, and immobilization. For operative treatment, a combination of procedures, including Achilles tendon lengthening, gastrocnemius recession, flexor digitorum longus tendon transfer, arthroereisis, and several methods of osteotomies and arthrodeses, have been extensively advocated in orthopedic (
Adult acquired flexible flatfoot, treated by calcaneocuboid distraction arthrodesis, posterior tibial tendon augmentation, and percutaneous Achilles tendon lengthening: a prospective outcome study of 20 patients.
The use of tricortical autograft versus allograft in lateral column lengthening for adult acquired flatfoot deformity: an analysis of union rates and complications.
Complex reconstruction for the treatment of dorsolateral peritalar subluxation of the foot: early results after distraction arthrodesis of the calcaneocuboid joint in conjunction with stabilization of, and transfer of the flexor digitorum longus tendon, to the midfoot to treat acquired pes planovalgus in adults.
). Historically, tricortical iliac crest autografts and allografts have been chosen as bone graft materials for CCDA, and comparisons of the use of autografts versus allografts have been described in orthopedic studies (
The use of tricortical autograft versus allograft in lateral column lengthening for adult acquired flatfoot deformity: an analysis of union rates and complications.
Randomized prospective study comparing tri-cortical iliac crest autograft to allograft in the lateral column lengthening component for operative correction of adult acquired flatfoot deformity.
Adult acquired flexible flatfoot, treated by calcaneocuboid distraction arthrodesis, posterior tibial tendon augmentation, and percutaneous Achilles tendon lengthening: a prospective outcome study of 20 patients.
Adult acquired flexible flatfoot, treated by calcaneocuboid distraction arthrodesis, posterior tibial tendon augmentation, and percutaneous Achilles tendon lengthening: a prospective outcome study of 20 patients.
) observed nonunion after using a tricalcium phosphate (TCP) block in an adult male weighing 110 kg. Although bone graft substitutes have been successfully used in around-the-knee osteotomies (
Adult acquired flexible flatfoot, treated by calcaneocuboid distraction arthrodesis, posterior tibial tendon augmentation, and percutaneous Achilles tendon lengthening: a prospective outcome study of 20 patients.
). Recent studies have revealed that combinations of rigid plate fixation with some types of hydroxyapatite or β-TCP wedges are useful for supramalleolar osteotomy without fibular osteotomy (mortise-plasty) in treating asymmetric ankle osteoarthritis with varus talar tilt (
In the present study, we report our experience with the use of newly developed rigid β-TCP wedges for the correction of AAFD to better understand the outcomes of this bone grafting procedure. We hypothesized that the use of β-TCP wedges would have similar clinical and radiographic results to those of historic controls of iliac crest autografts and allografts in CCDA. To the best of our knowledge, the present study is the first case series of this type reported.
Patients and Methods
Patients
From June 2012 to August 2015, a total of 13 feet in 13 patients underwent CCDA with synthetic bone grafts. These procedures were all performed by the first author (H.K.) at Fujieda Heisei Memorial Hospital. One male (7.69%) and 12 female (92.31%) patients with a mean age of 65.07 ± 11.83 (range 36 to 77) years were followed up for a mean duration of 32.76 ± 12.81 (range 18 to 55) months (Table 1). Our institutional review board approved the present retrospective case study (approval no. FHR-26-4), and all the patients provided written informed consent for inclusion.
Table 1Patient demographics (N = 13 feet in 13 patients)
Of the 13 patients, 1 (7.69%) had depression and 1 (7.69%) had type 2 diabetes (Table 1). Also, 2 patients (15.38%) had varus ankle osteoarthritis with peritalar instability (non-PTTD). No patient had undergone previous operative treatment in the affected lower limb; however, 1 patient (7.69%) had undergone contralateral distal first metatarsal osteotomy for hallux valgus correction 7 months after CCDA.
The clinical outcome measures included a 10-cm visual analog scale (VAS) for pain and the American Orthopaedic Foot and Ankle Society (AOFAS) Ankle-Hindfoot scale score. The results were classified as excellent for scores >90 points, good for score of 80 to 89, fair for scores of 70 to 79, and poor for scores <70. These clinical assessments were performed preoperatively and approximately once every 6 months postoperatively. The preoperative and most recent follow-up clinical outcome variables were compared in the present study.
Weightbearing anteroposterior, oblique, lateral, and hindfoot alignment radiographs were taken of each patient, and all feet showed flatfoot deformities with concomitant forefoot abduction. The radiographic outcome variables included the talonavicular coverage angle, first metatarsal talar angle, calcaneal pitch, and heel alignment angle (
). A smaller negative heel alignment angle indicated a greater lateral or valgus deviation of the calcaneus (Fig. 1). Although 2 patients (15.38%) had supramalleolar and intraarticular varus deformities (ie, non-PTTD), all 13 patients had inframalleolar valgus deformities. In the non-PTTD patients, mortise-plasty osteotomy was performed as a supplementary procedure to address the supramalleolar and intraarticular varus deformities (
Fig. 2Anteroposterior and hindfoot alignment radiographs of a 59-year-old female with flexible flatfoot deformity associated with varus ankle osteoarthritis and peritalar instability: (A and B) preoperatively and (C and D) 29 months postoperatively. Note that mortise-plasty osteotomy addressed the supramalleolar and intraarticular varus deformities, and calcaneocuboid distraction arthrodesis corrected the inframalleolar valgus deformities.
The patients underwent radiographic evaluation at regular intervals postoperatively. The most recent follow-up radiographs were analyzed to evaluate for correction of the preoperative flatfoot deformity. Rapideye Core software (Toshiba Medical Systems, Tokyo, Japan) was used as the image measurement device. Successful graft union was considered to have occurred clinically if local pain was absent during ambulation and, radiographically, if both intact osteosynthesis material and synthetic bone graft were documented. In contrast, serial radiographs manifesting broken hardware, loss of correction, and absorption of graft materials were considered to indicate nonunion. To avoid potential bias, 2 independent observers (Y.K., Y.S.), who were unaware of the study objectives, performed all clinical and radiographic evaluations.
Operative Technique
All surgeries were performed with the patient under general anesthesia and a continuous lumbar epidural block for postoperative pain control. The patients were placed in the supine position on the operating table with a pneumatic tourniquet applied to the thigh. An approximately 3-cm longitudinal incision was made over the calcaneocuboid joint just dorsal to the peroneal tendons. The extensor digitorum brevis muscle belly was then sharply dissected, with care taken not to damage the sural nerve traversing the operative site. In most cases, the peroneal tendon sheath was split longitudinally, and the tendons were retracted plantarly. The joint was exposed, and the articular surfaces of both the anterior calcaneus and the proximal cuboid were resected (approximately 2-mm wide) with a sagittal saw, irrigating frequently to avoid thermal necrosis. The arthrodesis site was repeatedly drilled to provide enhanced bone graft incorporation. A small laminar spreader was placed inside the joint. Under fluoroscopic guidance, distraction of the bone surface was performed until adequate reduction of the flatfoot deformity was confirmed. Two rigid β-TCP wedges (Superpore EX; HOYA Technosurgical, Tokyo, Japan) were cut into a truncated trapezoidal shape and were then inserted into the defect in a press-fit manner (Fig. 3). The newly developed wedge, which was originally devised as an opening wedge in high tibial osteotomy, had a porosity of 57% and compression strength of 48 MPa. The basic size of the wedge was 10-mm wide, 45-mm long, and 7- to 15-mm high (1-mm increments). The length of the wedge could be easily adjusted during surgery using a micro-bone saw or rongeur. Generally, we cut the wedges to 15 to 20 mm long to accommodate the depth of the joint. The mean graft height used in the present study was 11.0 ± 1.08 (range 10 to 13) mm (Table 1). At our institution, 2 β-TCP wedges cost approximately $750 compared with an autologous iliac crest bone graft, which costs $1170. A rigid locking plate (UPS; Wright Medical, Memphis, TN) was placed in a suitable position and secured with 3.5-mm screws. Two osteotomy staples (Orthomed, Côte d'Azur, France) were used in 1 patient (7.69%).
Fig. 3Intraoperative photograph showing 2 β-tricalcium phosphate wedges inserted into the arthrodesis site in a press-fit manner.
All 13 patients underwent ≥1 concomitant procedure, including flexor digitorum longus transfer to the navicular in 6 (46.15%), distal first metatarsal osteotomy in 5 (38.46%), medial displacement calcaneal osteotomy and mortise-plasty osteotomy in 2 each (15.38%), and syndesmosis repair, second metatarsocuneiform joint arthrodesis, talonavicular joint arthrodesis, and second metatarsal shortening osteotomy in 1 patient each (7.69%; Table 1). No patients, except for 2 (15.38%), who had undergone scheduled plate removal of the distal tibia 4 and 7 months apart, had undergone staged procedures. Platelet-rich plasma was not used in any of the patients.
Postoperative Management
Immobilization of the patients' legs was achieved using a non-weightbearing short cast for 8 weeks after surgery. Subsequently, they began progressive increased weightbearing with custom arch support insoles for another 4 weeks. After 12 weeks, full-weight single-crutch walking was often permitted, as tolerated. The patients were able to resume normal activities with regular shoes approximately 5 months after surgery.
Statistical Analysis
Statistical analysis of the descriptive data was performed using the Wilcoxon signed-rank test with a level of significance set at p < .05. The Statcel 4 software package (OMS Publishing Inc, Saitama, Japan) was used to analyze the raw data.
Results
Of the 13 patients, 12 (92.31%) obtained uneventful bone union. Also, 12 patients (92.31%) had pain relief and improvement in walking ability after CCDA with synthetic bone grafts. However, we could not determine the exact timing of the radiographic union. This was in part because most arthrodesis sites showed primary or direct healing without callus formation and in part because a limited number of postoperative radiographs were taken. Although successful graft union was radiographically confirmed, 1 patient (7.69%) showed no clinical improvement. In all patients, remnants of the β-TCP wedges were still clearly visible at the latest follow-up visit.
The mean VAS and AOFAS ankle-hindfoot scale scores preoperatively were 7.97 ± 1.52 (range 5.4 to 10) and 54.46 ± 14.72 (range 18 to 75), respectively. Postoperatively, the VAS and AOFAS ankle-hindfoot scale scores had improved to 1.52 ± 1.78 (range 0 to 6.2) and 85.46 ± 13.38 (range 50 to 97), respectively (p = .001 for both comparisons). The overall results of the AOFAS scale score were excellent in 5 feet (38.46%), good in 6 (46.15%), and poor in 2 (15.38%). Six patients (46.15%) used custom arch support insoles in fashionable shoes at the latest follow-up period. Ten patients (76.92%) were either satisfied or very satisfied with the end results and stated they would choose the same procedure again (Table 2).
Complications included implant-related pain and nonunion in 1 patient (7.69%) each (Table 1). The former patient underwent unplanned plate removal at 17 weeks after the initial surgery and achieved adequate pain relief. The latter patient was found to have broken hardware, loss of correction, and absorption of graft materials 14 weeks after surgery (Fig. 4). However, no additional surgery was required for this patient because the nonunion was clinically asymptomatic. Except for this nonunion case, no delayed graft fractures occurred during the follow-up period.
Fig. 4Lateral weightbearing radiograph of the left foot taken 33 months postoperatively showing broken hardware, loss of correction, and absorption of graft materials.
The mean preoperative talonavicular coverage angle, first metatarsal talar angle, calcaneal pitch, and heel alignment angle were 21.76° ± 5.49° (range 15° to 34°), 17.76° ± 4.47° (range 10° to 25°), 11.76° ± 3.16° (range 5° to 17°), and −12.38° ± 4.09° (range −20° to −4°), respectively. At the most recent follow-up visit, the corresponding values were 9.46° ± 3.28° (range 3° to 15°), 13.0° ± 4.16° (range 6° to 23°), 17.46° ± 6.23° (range 3° to 27°), and −6.07° ± 6.08° (range −13° to 8°; p = .001, p = .028, p = .006, and p = .001, respectively; Table 3). One patient (7.69%) in whom 11-mm wedges had been used might have had a somewhat overcorrected foot (ie, heel alignment angle >5°). However, this patient had not reported any pain or discomfort along the lateral column at the latest follow-up visit. None of the patients had developed arthrosis or subluxation in the fifth metatarsocuboid joint at the latest follow-up examination. The radiographic outcomes are shown in Fig. 5.
Fig. 5Anteroposterior, lateral, and hindfoot alignment radiographs of a 73-year-old female with flexible flatfoot deformity associated with hallux valgus deformity: (A to C) preoperatively and (D to F) 23 months postoperatively.
Fig. 5Anteroposterior, lateral, and hindfoot alignment radiographs of a 73-year-old female with flexible flatfoot deformity associated with hallux valgus deformity: (A to C) preoperatively and (D to F) 23 months postoperatively.
Bone grafting is essential for repair of nonunion, arthrodesis, tumor resection, and some fracture treatments. Four types of bone grafts are available: autografts, allografts, xenografts, and bone graft substitutes. To date, both autograft and allograft tricortical iliac crest bone grafts have been commonly used, with promising results (
Adult acquired flexible flatfoot, treated by calcaneocuboid distraction arthrodesis, posterior tibial tendon augmentation, and percutaneous Achilles tendon lengthening: a prospective outcome study of 20 patients.
). The use of allografts can decrease the operative time and eliminate the risk of any donor site morbidity. However, allografts increase the risk of a prolonged incorporation time and possible disease transmission. Moreover, allografts are often not commercially available in some countries owing to the high costs, lack of approval for use, or religious reasons (
Adult acquired flexible flatfoot, treated by calcaneocuboid distraction arthrodesis, posterior tibial tendon augmentation, and percutaneous Achilles tendon lengthening: a prospective outcome study of 20 patients.
) described the first case of successful graft union in a 26-year-old male who, 2 years previously, had sustained a calcaneal fracture with resultant shortening along the lateral column. In their report, a coralline hydroxyapatite block (ProOsteon®, Biomet, Inc, Warsaw, IN) was used at the calcaneocuboid joint to achieve distraction. However, they recommended not using a block for any distraction procedure of the foot because of the graft's structural weakness. According to a radiographic study by Sartoris et al (
), coralline hydroxyapatite does not possess the strength of trabecular bone or plastic properties because it lacks a collagen matrix. However, over time, with bone ingrowth, the graft substitute will become stronger but less stiff than the autograft (
Adult acquired flexible flatfoot, treated by calcaneocuboid distraction arthrodesis, posterior tibial tendon augmentation, and percutaneous Achilles tendon lengthening: a prospective outcome study of 20 patients.
The use of tricortical autograft versus allograft in lateral column lengthening for adult acquired flatfoot deformity: an analysis of union rates and complications.
Complex reconstruction for the treatment of dorsolateral peritalar subluxation of the foot: early results after distraction arthrodesis of the calcaneocuboid joint in conjunction with stabilization of, and transfer of the flexor digitorum longus tendon, to the midfoot to treat acquired pes planovalgus in adults.
) reported the greatest successful fusion rate of 93.75% (15 of 16 feet) after CCDA using autogenous tricortical bone block harvested from the iliac crest. However, because of the complication rates, clinical outcomes, and patient satisfaction, they recommended lateral column lengthening using calcaneal lengthening osteotomy rather than CCDA for the correction of stage II PTTD. In their prospective trial study, Gutteck et al (
Adult acquired flexible flatfoot, treated by calcaneocuboid distraction arthrodesis, posterior tibial tendon augmentation, and percutaneous Achilles tendon lengthening: a prospective outcome study of 20 patients.
) also reported good success rates (88.23% [15 of 17 feet] and 90.0% [18 of 20 feet], respectively), with autologous iliac crest bone grafts. However, van der Krans et al (
Adult acquired flexible flatfoot, treated by calcaneocuboid distraction arthrodesis, posterior tibial tendon augmentation, and percutaneous Achilles tendon lengthening: a prospective outcome study of 20 patients.
Adult acquired flexible flatfoot, treated by calcaneocuboid distraction arthrodesis, posterior tibial tendon augmentation, and percutaneous Achilles tendon lengthening: a prospective outcome study of 20 patients.
The use of tricortical autograft versus allograft in lateral column lengthening for adult acquired flatfoot deformity: an analysis of union rates and complications.
) reported an overall union rate of 78.78% (26 of 33 feet) using tricortical crest autografts and allografts. They reported a greater union rate of 91.3% (21 of 23 feet) with allografts supplemented with platelet-rich plasma compared with 50.0% (5 of 10 feet) using autografts. However, on average, the cost of an allograft procedure with supplemental platelet-rich plasma was approximately $2315 more than that of an autograft procedure. Dolan et al (
Randomized prospective study comparing tri-cortical iliac crest autograft to allograft in the lateral column lengthening component for operative correction of adult acquired flatfoot deformity.
Complex reconstruction for the treatment of dorsolateral peritalar subluxation of the foot: early results after distraction arthrodesis of the calcaneocuboid joint in conjunction with stabilization of, and transfer of the flexor digitorum longus tendon, to the midfoot to treat acquired pes planovalgus in adults.
), 8 of 41 feet (19.51%) developed nonunion (ie, union rate of 80.49%) after CCDA using autogenous iliac crest bone grafts. They used 2 crossed screws as their initial method of fixation (union rate of 76.47%); however, subsequently 7 of 7 feet (100%) achieved fusion when they used a rigid locking H plate.
Adult acquired flexible flatfoot, treated by calcaneocuboid distraction arthrodesis, posterior tibial tendon augmentation, and percutaneous Achilles tendon lengthening: a prospective outcome study of 20 patients.
The use of tricortical autograft versus allograft in lateral column lengthening for adult acquired flatfoot deformity: an analysis of union rates and complications.
Complex reconstruction for the treatment of dorsolateral peritalar subluxation of the foot: early results after distraction arthrodesis of the calcaneocuboid joint in conjunction with stabilization of, and transfer of the flexor digitorum longus tendon, to the midfoot to treat acquired pes planovalgus in adults.
). They concluded that the greater nonunion rate was explained by the insufficient rigidity of the fixation with a 3-hole one-third tubular plate. Therefore, the use of rigid locking fixation, which prevents or lessens the collapse of the graft, was strongly recommended (
) also reported a very high rate of nonunion (15 of 32 feet [46.87%]) after CCDA using an autogenous tricortical iliac crest graft. They found 2 different types of failure at the arthrodesis site (
). One was a classic nonunion, which maintained the structural integrity of the graft, and the other included osteolysis and collapse of the graft with the nonunion. They hypothesized that the high rate of failure resulted partly from high forces and weakening of the bone graft as it underwent revascularization and remineralization (
However, we achieved graft incorporation in 12 of 13 feet (92.31%) after CCDA with synthetic bone grafts. Although the number of subjects was small and the follow-up period short, our results seemed comparable, if not superior, to the cited results (
Adult acquired flexible flatfoot, treated by calcaneocuboid distraction arthrodesis, posterior tibial tendon augmentation, and percutaneous Achilles tendon lengthening: a prospective outcome study of 20 patients.
The use of tricortical autograft versus allograft in lateral column lengthening for adult acquired flatfoot deformity: an analysis of union rates and complications.
Complex reconstruction for the treatment of dorsolateral peritalar subluxation of the foot: early results after distraction arthrodesis of the calcaneocuboid joint in conjunction with stabilization of, and transfer of the flexor digitorum longus tendon, to the midfoot to treat acquired pes planovalgus in adults.
). We believe that our use of the newly developed rigid β-TCP wedges, which possess a relatively high porosity of 57% and compression strength of 48 MPa, had an important effect on the outcomes. The β-TCP block with 57% porosity has a compression strength that is approximately 2.5 times greater than that of a conventional hard type β-TCP block with 60% porosity (20 MPa) (
Bone formation and resorption in patients after implantation of beta-tricalcium phosphate blocks with 60% and 75% porosity in opening-wedge high tibial osteotomy.
J Biomed Mater Res B Appl Biomater.2008; 86: 453-459
). Furthermore, this value (48 MPa) is close, if not equal, to that of human cortical bone, whose compression strength has been reported to be 100 to 150 MPa for the longitudinal direction and ≤50 MPa for the transverse direction (
), when the graft begins to heal or incorporate, it has a propensity to collapse. Therefore, the high compression strength of β-TCP wedges might have helped to prevent or lessen this problem.
In our patient cohort, 1 patient (7.69%) was noted to have broken hardware and developed asymptomatic nonunion. However, the patient did not express any discomfort or pain around the calcaneocuboid joint. The exact reason for this clinical improvement remains unknown. However, our view is that pain relief was obtained by the realignment and stabilization of the arthritic ankle with the mortise-plasty osteotomy (
) and the unintended resection–interposition arthroplasty (ie, pseudoarthrosis) of the painful calcaneocuboid joint. The patient was very satisfied with the postoperative pain relief and subsequently underwent contralateral distal first metatarsal osteotomy 7 months after the initial surgery. No other adverse events regarding the use of synthetic bone grafts had been noted at the last follow-up examination.
The present study had some limitations and weaknesses. The first was the small number of subjects and relatively short follow-up period. We admit that studies of bone graft substitutes require longer follow-up periods because complete resorption of the β-TCP wedges had not occurred at our maximum follow-up period. Over time, additional further nonunions might develop, which would greatly increase our failure rates. The second limitation was the use of concomitant surgical procedures. All patients underwent additional bony and/or soft tissue procedures that could have affected the postoperative clinical and radiographic outcomes. We could not determine to what degree the changes had resulted from the CCDA versus the other procedures. Furthermore, the effects of the adjunctive procedures on the union rate remain unknown. Finally, the third was the retrospective study design and lack of inclusion of a comparative group. Despite these limitations, the postoperative clinical results and complication rates seemed acceptable in the short term; thus, we believe that this grafting procedure deserves to be considered in future studies.
In conclusion, the use of synthetic bone graft substitutes is a viable option for the treatment of AAFD. The precut design allows the surgeon to perform an exact predetermined amount of distraction at the arthrodesis site. It also eliminates any possible donor site morbidities. However, we believe that the described method is even more challenging than the conventional methods because the long-term durability of this specific form of bone graft is unclear and, hence, should be used with caution. In the present cohort, we used rigid locking fixation and prolonged non-weightbearing with success; however, they were not compared with conventional fixation and/or early weightbearing. Although good clinical and radiographic results were obtained in our small patient cohort, our findings should be considered preliminary, and additional studies are required.
Adult acquired flexible flatfoot, treated by calcaneocuboid distraction arthrodesis, posterior tibial tendon augmentation, and percutaneous Achilles tendon lengthening: a prospective outcome study of 20 patients.
The use of tricortical autograft versus allograft in lateral column lengthening for adult acquired flatfoot deformity: an analysis of union rates and complications.
Complex reconstruction for the treatment of dorsolateral peritalar subluxation of the foot: early results after distraction arthrodesis of the calcaneocuboid joint in conjunction with stabilization of, and transfer of the flexor digitorum longus tendon, to the midfoot to treat acquired pes planovalgus in adults.
Randomized prospective study comparing tri-cortical iliac crest autograft to allograft in the lateral column lengthening component for operative correction of adult acquired flatfoot deformity.
Bone formation and resorption in patients after implantation of beta-tricalcium phosphate blocks with 60% and 75% porosity in opening-wedge high tibial osteotomy.
J Biomed Mater Res B Appl Biomater.2008; 86: 453-459
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