The Use of Allograft Prosthesis Composite for Extensive Proximal Femoral Bone Deficiencies

The Journal of Arthroplasty Vol. 24 No. 8 2009

The Use of Allograft Prosthesis Composite for Extensive Proximal Femoral Bone Deficiencies A 2- to 9.8-Year Follow-Up Study Soo H. Lee, MD,* Young J. Ahn, MD,* Sae J. Chung, MD,* Byeong K. Kim, MD,y and Ji H. Hwang, MDz

Abstract: We report here results for 15 hips that we repaired using allograft prosthesis composite (APC) and monitored for a mean of 4.2 years. Two hips underwent repeat revisions with new APCs after a mean of 83.7 months. The average Harris Hip Score improved from 21.8 before revision surgery to 83.2 afterward, and 12 stems showed good stability. Of the 15 hips repaired with APC, 13 had good junctional union. One of the 2 remaining hips showed nonunion, which was repaired with an onlay graft 3.3 years later, and the other hip showed both infection and nonunion. There was 1 dislocation, and 2 hips had complications related to the greater trochanter. Our findings demonstrate that the use of APC produces satisfactory results. Keywords: proximal femur, allograft prosthesis composite, femoral bone deficiency, hip arthroplasty. Crown Copyright © 2009 Published by Elsevier Inc. All rights reserved.

The number of hip joint arthroplasties has steadily been increasing since the early 1990s. The number of revision procedures has been increased proportionately. Because of the lack of correct and early diagnoses, more joint arthroplasties were performed on Korean adults than Westerners of the same age [1]. Lack of early treatment resulted in sequelae that necessitated joint arthroplasty. Accordingly, there are more cases in Korea of revision surgery in much younger patients than in the West. Most of the patients requiring revision surgery have severe bone defects, making the procedure challenging and problematic. Currently, these defects, caused by osteolysis and loosening, are revised with the use of impact grafting, revision stem, megaprosthesis, onlay strut graft, and allograft prosthesis composite (APC), and many authors have reported good results with these materials and techniques [2-6]. The major

From the *Department of Orthopedics in Asan Medical Center, Ulsan University, College of Medicine, Seoul, South Koreal; yDepartment of Orthopedic Surgery, Haemin Hospita, Hallym University, College of Medicine, Seoul, South Koreal; and zDepartment of Orthopedics, Kangnam Sacred Heart Hospital, Hallym University, College of Medicine, Seoul, South Korea. Submitted February 5, 2009; accepted June 6, 2009. No benefits or funds were received in support of the study. Reprint requests: Ji H. Hwang, MD, Department of Orthopedics, Kangnam Sacred Heart Hospital, Hallym University, College of Medicine, 948-1 Daerimdong, Yeongdeungpogu, Seoul 150-950, South Korea. Crown Copyright © 2009 Published by Elsevier Inc. All rights reserved. 0883-5403/09/2408-0020$36.00/0 doi:10.1016/j.arth.2009.06.006

burdens in APC are coping with technical difficulties and disease transmission, resorption, nonunion, and fracture of the allograft-fall to the surgeon. The benefits of using APC include restoration of bone stock, provision of a biologic anchor for attachment of the abductor tendon, biologic fixation, ease of rerevision, provision of an ideal bone-cement interface, load sharing after union, and the ability to precisely adjust graft length [1]. In our institution, however, we have encountered several difficulties in using allograft: first, cadaveric donors are not readily available in Korea because it is not culturally acceptable to donate one's body to science. Therefore, when we want to use allogeneic bone, we must consider its tremendous cost because all allogeneic bone used in Korea is imported from other countries. Second, most Koreans are highly concerned about the transmission of diseases, especially AIDS, making allograft use unacceptable to many patients. Third, size mismatch and immune rejection of the allogeneic bone, which is usually imported from the United States, is sometimes a problem. Therefore, we restrict the use of allogeneic bone to certain situations. Since 1996, the senior author (SH Lee) has performed more than 140 revision hip arthroplasties; only 15 of which used large femoral allograft prosthesis constructs. We describe here a surgical technique for using proximal femoral allografts and present radiographic and clinical results from our early experience with the technique.

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Materials and Methods Patients and Follow-Up Monitoring Between January 1996 and December 2006, we treated 15 patients with APC total hip prostheses, and 2 of them had undergone re-revision surgery with new APCs; they were monitored for an average of 4.2 years (range, 2-9.8 years). Those who were monitored for a minimum 2 years were retrospectively reviewed. There were 7 men and 8 women, and their average age was 60.9 years (range, 32-84 years) at the time of follow-up evaluation. Two patients had already undergone revision arthroplasties with proximal femoral allografts, all because of aseptic loosening. We replaced all acetabular and femoral components during surgery. We used ceramic-on-ceramic liners in 8 instances and metal-on-polyethylene in 7. In most cases (8), we used Lima-Lto revision stems (Lima-Lto, Udine, Italy); we used an MP reconstruction stem (Waldemar-Link, Hamburg, Germany) in 3, an S-ROM revision stem (DePuy, Warsaw, Ind) in 2, and a Restoration stem (Stryker, Mahwah, NJ) in 2. We chose the implant randomly without any preference of stem design, regardless of abnormal bone geometry. Aseptic loosening was a major cause of index revision (8 cases). In 6 cases, the diagnosis was septic loosening, and in 1 case, the diagnosis was malignancy (malignant fibrohistiocytoma) in the proximal femur. Among the 8 hips revised for aseptic loosening, there were 2 repeat revisions with new APCs. All allografts, supplied by the Junyoung Medical Company, Seoul, Korea, and stored at −79°C, were imported through Community Tissue Service (Dayton, Ohio). All allografts were screened for transmissible diseases, including HIV and hepatitis. The average length of the proximal femoral allograft used in surgery was 9.6 cm (range, 6.9-12.7 cm). We classified femoral defects by findings on preoperative plain radiographs and intraoperative findings, using the American Academy of Orthopaedic Surgeons classification system [7]. We encountered 1 case of segmental defect, 7 cases of cavitary defect, 7 cases of combined defect, and no cases of femoral discontinuity. However, our treatment option of APC for reconstruction of bone defects was not dependent on this classification. We routinely used prophylactic antibiotics (cephalosporins) before and during surgery and continued administering them for 10 days afterward; we then administered them orally for 7 additional days. In some cases of revision of septic loosening, however, we administered broader-spectrum antibiotics such as vancomycin or teicoplanin intravenously for 14 days. We also routinely used prophylactic anticoagulation, in the form of low molecular-weight heparin (Lovenox [enoxaparin sodium]): 40 mg subcutaneously just before surgery and then continued at 40 mg/d for 1 week after surgery.

Surgical Technique All surgeries were performed from the posterolateral approach by the same surgeon (S.H. Lee), with patients in the lateral decubitus position and using the incision from the previous procedure whenever possible. The transtrochanteric approach was used routinely for removal of the stem and extensive exposure. In 11 cases, we used the standard trochanteric osteotomy; for the other 4, we performed an extended trochanteric osteotomy to remove cemented stems or firmly fixed stems. After dislocation of the joint, we removed cemented or cementless stems meticulously and prepared the acetabular bed with the insertion of jumbo cups, polyethylene cups over cement mantles, or reinforcement cages, as dictated by the bone stock. Bone defects of the acetabular bed were estimated intraoperatively and reconstructed with morselized bones or whole distal femoral allografts, secured with screws. In 4 cases in which the contact area of acetabular bed with a trial cup was more than 60%, we did not reconstruct the defect. In 6 cases, centralized defects were reconstructed with morselized bones; in 5 cases, peripheral defects were augmented with whole distal femoral allografts, especially in the superolateral portion of the acetabulum. All allografts were obtained from our institution's tissue bank, where they had been stored at −80°C. Graft diameter was selected carefully, using preoperative radiographs for size matching. We regard the fit of the prosthetic stem as good when the cement mantle was acceptable. Therefore, the donors of allografts who were chosen were much taller and larger than the recipients. Allograft length, which varied from 6.9 to 12.7 cm (average, 9.6 cm), was determined after preparation of the host bone, and we tried to retain as much of the host bone that was attached surrounding musclesas possible. The shortest allograft that we used was 6.9 cm long when we encountered a huge defect of the greater trochanteric area after trochanteric osteotomy and relatively well-preserved bone stock in the distal area. We considered provision of a biologic anchor for attachment of the abductor tendon in that case. All stems were cemented into the allograft with CMW 1 medium-viscosity, gentamicin-loaded bone cement (DePuy). The allograft was reamed until a good fit for the implant was achieved, allowing for a cement mantle around the stem of a thickness of at least 2 mm. When we inserted the real implant, we wrapped the distal portion of the stem with an Ioban drape (3M Korea, Seoul, Korea) to prevent staining the real implant with cement. After insertion of the real implant, the cement-stained drape was removed. Cement mixing was assisted by vacuum and pressurized with fingers. In the early period of our series, 3 implants were cemented in the distal host bone because we were not accustomed to this technique and because we were concerned about insufficient bone stock for distal-fit fixation. The junction between allograft and

APC for Extensive Proximal Femoral Bone Deficiencies  Lee et al

host bone was transverse cut in the 9 hips that were found to be stable intraoperatively, but 6 hips were carefully step cut because of concerns about stability and bone-allograft union. Although the step cut is more stable than the transverse cut, it is technically demanding, which limits its routine use. The length of the revision stem was determined after consideration of distal host bone stability. For stability, we aimed for a contact area of 10 cm minimally from the distal of the bone-allograft junction [8-10]. If we had been able to use the modular femoral stem (Lima-Lto revision stem) that was assembled with proximal and distal components, we might have been better able to match stem length and anteversion, but bone defects could not be repaired without augmentation or bone graft in our cases. We gathered bone debris from the host bone after reaming for autografting on the osteotome site. When the autogenous bone graft was insufficient, we used synthetic bone material such as MIIG injectable graft (Wright Medical Technology, Inc, Arlington, Tenn) in 3 cases. Cortical strut onlay allograft was routinely used to stabilize the osteotome site at the bone-allograft junction, which was tightened with Dall-Miles cables [11,12]. We used cementless revision stems in all hips, but we cemented 3 because of poor bone quantity and quality. Reinsertion of the abductor musculature was the one of the key steps during surgery. For this process, we used 3 different techniques. If the remaining proximal bone fragment was large and dense enough (10 hips), we fixed the fragment with previously placed wires and additional cerclage cables [10]. If bone size and quality were not sufficient (1 hip), we used a grip plate (APIS cable and sleeve system, Tradimemics, Sungnam, Korea). If the remaining bone of the greater trochanter was sacrificed and could not be reattached to the femur (4 hips), we sutured it tightly with absorbable sutures. Patients were hospitalized for at least 4 weeks (range, 4-14 weeks) and required to maintain bed rest and to use a wheelchair for 4 weeks. At that point, they began 6 weeks of movement involving no weight bearing on the repaired hip, and then weightbearing as tolerated was allowed until there was evidence of bone–allograft union, usually at 3 to 6 months after surgery.

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radiolucent lines around the junction. Nonunion was not diagnosed until at least 1 year without further progress toward union had passed [14]. Trochanteric union was defined as a lack of migration of the great trochanter, with trabecular bridging; migration or a gap of more than 1 cm was regarded as nonunion [15]. Migration of less than 1 cm from the original bed was considered to be fibrous union. We regarded the loosening of the component to be subsidence of the stem of more than 3 mm, fracture of the cement mantle, or progressive changes in radiolucent lines around the stem. We began checking radiographs for a change in the interval between graft and bone at 6 weeks after surgery. In some patients, union occurred at a point somewhere between 4 and 16 months (average, 11.6 months), but in most patients, it occurred at a point between 6 and 12 months (Fig. 1). Two of 15 patients (13.3%) had nonunion at the bone-allograft junction. In one of them, the hip was symptomatic enough to require more surgery (Fig. 2A). At 4.3 years after the first surgery, we performed an additional procedure, using plating and autografting, which produced complete union and good function (Fig. 2B). The lack of union in the other patient who was 71 years old at the time of the APC surgery due to the septic loosening was detected by delayed-onset infection and lack of evidence of a bridging callus. She had undergone total hip arthroplasty because of the femoral neck fracture and

Results Radiographic Analysis We performed radiographic assessment at 6 weeks, 3 months, and 6 months after surgery, and then annually. Routine anteroposterior and lateral radiographs were assessed for evidence of union at the junction of allograft and host bone, trochanteric union, endosteal and periosteal resorption, component loosening, and fracture. We defined the union at the allograft and host bone junction by radiographic evidence of blurring, with bridging trabeculae at the junction [13] and no

Fig. 1. Radiograph obtained 14 months after surgery shows a huge bridging callus on the medial side of bone-allograft junction. There is no evidence of loosening.

1244 The Journal of Arthroplasty Vol. 24 No. 8 December 2009

Fig. 2. (A) A radiolucent gap, indicating nonunion at the bone–allograft junction after repair with allograft prosthesis composite, is apparent. (B) This final follow-up radiograph from the same patient as in Figure A shows good union after the use of an onlay strut graft and autografting 4.3 years after the initial repair.

revision due to the aseptic looseing in the local clinic. Her symptoms and laboratory findings waxed and waned and she refused fourth replacement surgery at her 75-month follow-up examination. At press time, we observed with regular follow-up. We had 7 hips (46.6%) in which there was resorption, categorized as mild, moderate, or severe according to the thickness of bony involvement [16]: 3 (20%) with mild (partial) resorption of the allograft, 3 (20%) with moderate (about 50% loss of thickness) resorption, and 1 (6.7%) with severe (almost full thickness) resorption. Resorption was most common in Gruen zone 7 (5 hips) and zone 2 (1 hip), and 1 hip had resorption in both zones. Among these patients, 1 with severe resorption and 1 with moderate resorption were symptomatic and resorption was progressive, which meant that another round of revision surgery was required. We did repeated revisions using new APC at the follow-up points of 92 and 108 months, respectively. These hips showed good stability at the last follow-up examination. In analyzing

these cases of significant loosening and infected nonunion retrospectively, we realized that all of the stems in this series were cemented in the distal portion of host bone in the early period of experience in our clinic. We had not had much experience with host bone preparation at that time. Two hips had trochanter-related complications: 1 had trochanteric nonunion and 1 had avulsion fracture, which was related to minor trauma, at 15 months after surgery (Fig. 3). Although that particular patient is 58 years old, she has no pain or limping on the affected side, so at press time, we were still observing her. No patients underwent reoperation because of trochanteric problems because all of them found the pain tolerable and could function well. Clinical Evaluation We compared patients' preoperative modified Harris Hip Score (for which a score of b70 is poor, 70-79 is fair, 80-89 is good, and 90-100 is excellent) with their score at the last follow-up examination. The average

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Fig. 3. One year after surgery (left), a 58-year old woman's prosthesis was functioning well. Fifteen months later (right), she sustained a fragment avulsion. Note the broken wire on the greater trochanter.

preoperative score was 21.8 points (range, 12-55 points); the average postoperative score was 83.2 points (range, 67-96 points). The average increase in score was 34 points (range, 22-55 points). Most of the patients who were unsatisfied with the surgical results complained of pain and limping. In all cases, the abductor was reattached to the allograft, so we measured abductor muscle power. For the evaluation of abductor muscle power, we used manual testing, electromyelography, computed tomography for muscle volume, and an isokinetic dynamometer (Cybex II, Lumex, Ronkonkoma, NY). However, only the results of manual testing (grade 0-5) were recorded. The average postoperative grade was 4.4 (range, 3-5) without nerve palsy. This was an improvement over preoperative muscle power, for which the average grade was 3.9 (range, 3-5) [17]. Complications We divided complications into intraoperative and postoperative categories. During surgery, there was neither neurovascular injury nor increased duration of surgery related to unexpected problems such as fat embolism, coagulopathy, or pulmonary edema. However, 4 patients were transferred to an intensive care unit immediately

after surgery at the request of the anesthesiologist; all had been classified before surgery as being placed at high risk by undergoing anesthesia. They remained in the intensive care unit for 1 to 3 days until their vital signs and mental status were stabilized. In the early phase after surgery, there was no wound infection, deep vein thrombosis, or nerve paralysis. In the late phase after surgery, however, there were many complications, including loosening, nonunion, infection, fracture of the greater trochanter, and dislocation. As mentioned earlier, 2 hips (13.3%) had significant loosening of the stem, which was resolved by additional revision surgery with the same technique. In addition, nonunion was one of the most serious and worrisome complications: 2 hips (13.3%) had nonunion of the bone-allograft junction, and 1 hip (6.7%) had nonunion in the greater trochanter. Only 1 of the hips with boneallograft nonunion underwent additional revision surgery, and that was at 4.3 years after the original revision. One hip had delayed-onset deep infection (6.7%) related to the bone–allograft nonunion, which has been responsive to conservative treatment. One hip had avulsion fracture of the greater trochanter. Another patient experienced hip dislocation (6.7%) at 5 weeks after surgery; it was treated with an abduction brace for

1246 The Journal of Arthroplasty Vol. 24 No. 8 December 2009 Table 1. Local Complications after Femoral Allograft Complications Instability (loosening) Junctional nonunion Infected nonunion Greater trochanter nonunion Greater trochanter fracture Dislocation Overall

No. of Hips

Percentage (%)

No. of Reoperations

2

13.3

2

1

6.7

1

1 1(/11)

6.7 9

0 0

1(/11)

9

0

1 7

6.7 46.7

0 3 (20%)

6 weeks. There were no allograft or stem fractures (Table 1). We defined clinical success as a postoperative increase in the Harris Hip Score of greater than 20 points, a stable implant, and no need for additional surgery related to the allograft at the last follow-up examination [18]. We performed 3 additional surgeries (20%) because 2 hips had loosening and 1 had nonunion. Our success rate was 80% (12 of 15 hips) at an average of 4.2 years of follow-up monitoring. However, our overall complication rate was 46.7%, and 3 hips had significant complications requiring additional surgery. Considering the rate of union alone, the success rate was 86.7%, with only 1 hip requiring additional surgery to achieve union. Considering the technical drawbacks in our early series, we might have expected a higher success rate. The survival rate for APC was not as high as could have been desired, but the use of APC could be a good alternative for managing extensive femoral bone deficiency in revision arthroplasty.

Discussion After removing an implant in repeat joint-replacement surgery, the surgeon must deal with the increased loss of bone stock, which in turn contributes to early mechanical failure of the revised hip. The results of revision hip arthroplasty have not been as predictable as those of primary arthroplasty [1]. In Korea, the increasing number of revision cases provide more opportunities to use proximal whole allograft during surgery, but the cost, the possibility of transmission of diseases such as AIDS (which is not endemic to Korea), and the possibility of graft-host size mismatch or immune rejection make allograft surgery rare in Korea. Moreover, many Koreans mistakenly believe that disease can be transmitted by allogeneic bone, so because of patients' consequent refusal of allograft procedures, there were few performed in the early 1990s that could have provided surgeons with opportunities to gain experience. At that time, we preferred using revision long stems, modular stems, megaprostheses, or impaction grafting for hip revisions. Now, however, many Korean surgeons, influenced by reports of success from the United States and Europe, use

allografts for revision surgery when there is a huge bone deficiency. Consequently, the use of allografts is absolutely related to successful union at the graft-host bone junction. We achieved successful union in 13 (86.7%) of 15 hips. That is, the rate of nonunion was 13.7%. These results are comparable with those from other studies, which range from 3.5% to 23% [19-21]. The average time to union in our series was 11.6 months, with union usually occurring somewhere between 6 and 12 months. Even considering the problems of size mismatch and immune rejection before surgery, there was no complication that related to these problems. This suggests that there might not be any ethnic differences in considering immune rejection. To induce union at the graft-bone junction, we performed a step cut with an osteotome and grafted autologous bone debris or synthetic bone material in a few cases. In our series, 2 nonunions were related to the transverse cut, but we could not compare the union rate statistically because of the differing shapes of the osteotomes and the use of synthetic bone material. Among hips treated in this manner, we had 1 infected nonunion that created instability, making us realize that stem stability is important for achieving union with the allograft. Because infection in arthroplasty is serious, creating the need for additional surgery to control it, many surgeons focus on infection. However, in our series, there was only 1 instance of infection despite the length of surgery, extensive soft-tissue dissection, huge blood loss, and the patient's advanced age. Other studies have reported infection rates ranging from 0.3% to 20%, and the researchers involved performed one- or twostage repeat revision surgery to control infection [22,23]. However, the condition of our sole patient with infection is still responsive to conservative treatment; we did not perform a second revision to treat the infection. In the other hip with nonunion, we performed repeat revision surgery, using an onlay strut graft and autografting at 3.3 years after the first procedure, and that hip demonstrated good union and stability at the final follow-up examination. We cemented the proximal allograft in all cases, as other researchers have done, and we used cement for distal host stability in 3 hips that had had cementless stems in the early period of revision; the remaining 12 hips were stabilized with cementless revision long stems. The options for distal fixation have included distal cementing, distal interference fit [24], and interlocking fixation [25]. In the cementless stem, after accomplishment of union at the bone-allograft junction, the allograft also has a greater potential to share the weight bearing. It is difficult to remove cemented stems when necessary for infection management. Removal would be destructive to the remaining bone stock, so cement-related adverse effects such as cardiovascular toxicity must be overcome. We preferred using a cementless fit or locking stem, but because the junction is around or beyond the isthmus of the host femur, we were concerned about the security of fixation in the distal femur. In that situation, we

APC for Extensive Proximal Femoral Bone Deficiencies  Lee et al

cemented distal cementless stems, which resulted in resorption around the stems and loosening of all 3 cemented stems at an average of 83 months after surgery. We realize that this was the main technical drawback leading to stem failure. We saw 7 cases of resorption (46.6%); 1 hip had severe resorption, and 1 with moderate resorption underwent repeated revision because of symptoms and progression of radiologic change. This was a higher rate of resorption than has been previously reported [15,18]. Incidentally, all revised hips had been cemented to the distal host bone during earlier procedure. Head et al [25] classified the various results of revision hip arthroplasty by cemented versus cementless stems. Cemented stems had a rerevision rate of 5% to 20%, whereas cemented stems had a rate of 0% to 15%. There was no significant difference between the 2 groups, but there is no similar study comparing cemented stems and cementless stems in distal host bone in APC reconstruction. The etiology of a higher rate of loosening for cement augmented stems is likely that distal-cemented fixation leads to stress shielding, which leads to resorption due to the resulting mechanical disuse. Disintegration of the cement from the mattefinished surface of a cementless stem, not biologic loosening due to the immunogenicity of the allograft, creates early osteolysis and mechanical loosening. Two of the hips in our series had complications related to the greater trochanter: 1 had nonunion, and the other had an avulsion fracture. These patients were conservatively treated because their symptoms were tolerable. The rate of trochanteric nonunion has been reported to be between 25% and 45%. This is usually higher than the rate for nonunion at the bone-allograft junction because the traction power of the muscle is higher than the compression power of muscle in the trochanteric area [10,14]. At our institute, a rate of 13.3% for greater trochanter nonunion was considered satisfactory. One of the benefits of using allograft was the reattachment of soft tissue around the hip, which tensioned the abductor muscle and reduced dislocation. We analyzed muscle strength by manual testing at the final follow-up examination and found the average strength to be 4.4 on a scale of 0 to 5, which was satisfactory. Even though the Cybex test is regarded as one of the most objective and reliable tests for muscle strength, patients results on the test could not be compared because of the loss of some preoperative data. Zehr et al [26] reported the rate of megaprosthesis dislocation to be as high as 35%. However, only 1 hip (6.7%) in our series dislocated, 5 weeks after surgery, and this patient's condition was responsive to conservative treatment with an abduction brace for 6 weeks. It could be suggested that successful soft-tissue procedures and techniques such as reattachment of the abductor muscle reduced the rate of postoperative dislocation in our series, which was lower than for other series. Reconstruction of the proximal

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femur can be achieved successfully with either an endoprosthesis or APC. The use of an endoprosthesis is preferred by many Korean hip surgeons because of the difficulties involving in using allografts in Korea. However, we did not address the issues of disease transmission, bone–allograft nonunion caused by the host's immune system, or loosening. In 3 hips that underwent another surgery, they were transversely osteotomized without the use of synthetic material and were fixed with cement distal to the joint junction. In spite of the small number of cases in our series, we believed that our data show that step cut osteotomy and cementless distal fixation might have been factors that helped reduce the number of complications arising from the use of APC. Despite the inappropriate distal fixation of the prostheses, the overall survival rate of 80% at the midterm follow-up examination was comparable to others' findings and satisfactory for this group of patients. However, the 87.6% union rate achieved at 4.2 years of follow-up monitoring by our institute was very encouraging. To properly evaluate the results of using APC, however, we need to treat more hips and monitor them for a longer follow-up period.

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