Postoperative IL-6 levels cannot predict early onset periprosthetic hip/knee infections: an analysis of 7,661 patients at a single institution.

Prior studies have outlined C-reactive protein (CRP) within the first 5 d following total hip arthroplasty (THA) as an inappropriate indicator of an early periprosthetic joint infection (PJI). Recently, interleukin-6 (IL-6), as a potential inflammatory marker following total joint arthroplasty (TJA), has gained increasing interest, particularly due to its considerably shorter half-life. The aim of the present study was to assess IL-6 measured on postoperative day 3 following TJA as a prediction marker of early onset PJI. 7,661 patients, who underwent total hip or knee arthroplasty (THA, TKA) at a single institution between 2016 and 2019, were evaluated. Serum IL-6 values were measured on postoperative day 3 and compared between patients, with and without early onset PJI in the postoperative follow-up, matched for age, gender, Surgical Site Infection Risk Score and Charlson comorbidity index. Overall (n = 7,661), there was no statistically significant difference in serum IL-6 levels comparing patients with and without early onset PJI following THA [38.9 pg/ mL vs. 32.0 pg/mL, p = 0.116] and TKA [30.6 pg/mL vs. 28.2 pg/mL, p = 0.718]. Male gender and high body mass index were associated with an increased risk of early onset PJI following THA (p = 0.027, p = 0.002). Matched cohort analysis (n = 86) showed no statistically significant difference in serum IL-6 levels between patients with and without early onset PJI following THA (p = 0.680) and TKA (p = 0.910). Serum IL-6 values on postoperative day 3 following THA or TKA could not predict early onset PJIs.

Axial pelvic tilt in direct anterior Total hip Arthroplasty using a traction table.

BACKGROUND: Direct anterior approach total hip arthroplasty may be undertaken on a traction table, but the effects that patient positioning can have on axial pelvic tilt (aPT) are unknown. The aim of this study was to assess the degree of error from patient positioning on the traction table during anterior minimally-invasive surgery (AMIS) THA. METHODS: Patients were included who underwent direct anterior THA via the AMIS technique at a single institution between 11/2018 and 03/2019. Axial pelvic tilt was measured (a) in the supine position on the operating table, and (b) after positioning on the traction table, by the same consultant surgeon in all cases. RESULTS: In the above-mentioned study period, 50 patients (F: 32; M: 18) with an average age of 60.6 ± 13.6 (range: 26.5 to 88.3) years, and an average BMI of 27.2 ± 5.0 (range: 17.9 to 41.5) kg/m2 met the inclusion criteria. When measured in supine position, the average aPT was - 0.2 ± 1.7 (range: - 5.6 to 3.8) degrees. After positioning on the traction table, the average aPT was - 3.5 ± 2.1 (- 8.5 to 1.6) degrees (p < 0.001). In patients with an aPT of more than 5 degrees, the caput-collum-diaphyseal (CCD) angle was significantly lower (125 ± 11° vs. 134 ± 8°, p = 0.007). CONCLUSION: This study raises awareness for the potential risk of aPT during positioning of the patient on the traction table, commonly used during direct anterior THA via the AMIS technique.

Patient reported outcomes and implant survivorship after Total knee arthroplasty with the persona knee implant system: two year follow up.

BACKGROUND: More personalized implant designs for total knee arthroplasty might optimize the clinical outcome after surgery. One of these personalized implant designs is the Persona knee implant system (Zimmer Biomet, Warsaw, Indiana, USA). The primary objective of this study was to determine patient reported outcomes and implant survivorship of the Persona Knee system used in primary total knee arthroplasty, up to two years after surgery. METHODS: From November 2013 to July 2016 consecutive patients undergoing primary total knee arthroplasty were enrolled in a prospective observational cohort study at three centers. Preoperatively, at 6 weeks, 6 months, 1 and 2 years after surgery, patients completed the Knee Injury and Osteoarthritis Outcome Score (KOOS), the Oxford Knee Score (OKS), the Knee Society Score (KSS, 2011, modified version) and the EQ-5D. Adverse Events were captured, assessed for relationship to device, and recorded in the study database. Furthermore, physical functioning was assessed by the orthopedic surgeon. Repeated measures analyses were performed on PROM scores. Kaplan Meier was used to calculate survivorship of the Persona Knee Implant System. RESULTS: A total of 146 total knee arthroplasties were performed. 61% (89/146) of the patients were female and mean age was 64.7 (± 6.9) years. Two years after surgery, one patient had a revision of the polyethylene insert because of a periprosthetic joint infection. Therefore, the Kaplan-Meier survival estimate at 2 years was 0.99 (0.95-1.00 95% CI). OKS increased from 22.1 (95% CI 20.9-23.3) to 41.8 (95% CI 40.6-43.1) two years after surgery. Furthermore, all other PROMs also increased from before surgery to 2 year postoperatively. CONCLUSION: The Persona Knee implant is safe and effective and the clinical results up to two years after surgery are promising. PROMs results are very good; pain, function and quality of life all improved greatly after TKA. Further studies are needed to determine the long term clinical performance of the Persona prosthesis. TRIAL REGISTRATION: Clinicaltrials.gov ( NCT02337244 ). Registered June 1st, 2015. Retrospectively registered.

Pigmented villo-nodular synovitis and giant-cell tumor of tendon sheaths: a binational retrospective study.

AIM: Pigmented villonodular synovitis is rare. Thus, we initiated a retrospective multi-center study regarding symptoms, location, type of disease, type of surgery, number of recurrences, use of adjuvant therapies and functional outcome. RESULTS: Ten centers contributed. Data from 173 patients were sampled. The disease was seen predominantly in joints, less frequently in tendon sheaths and bursae. Patients with articular lesions suffered mainly from the diffuse type. In tendon sheaths, the relation "diffuse versus nodular" was nearly 50 % each, in bursae most often the nodular type was found. Anatomically, mostly the knee was affected. Institutions with more than 20 patients had a lower rate of recurrence than those with less than 20 cases. Regarding the knee, there were less recurrences in joints treated with open synovectomy than in those treated arthroscopically. CONCLUSIONS: Since the rate of recurrence has been rather high, the use of adjuvant treatments (radiosynoviorthesis or radiotherapy) is recommended. In our study, the rate of their application was quite low. Patients who received an adjuvant therapy after primary surgery did not show any recurrence. In 14 % of patients in whom an adjuvant therapy had been used, after at least one recurrence, further recurrences were observed. Functional results were excellent in 84 % of patients. LEVEL OF EVIDENCE: Prognostic multi-center study, Level III.

Imaging of highly malignant osteosarcoma with iodine-123-vascular endothelial growth factor.

OBJECTIVE: Vascular endothelial growth factor (VEGF) is an important angiogenic factor, and its receptors have been shown to be overexpressed in various human carcinomas. In this study, we investigated the role of scanning with iodine-123 ((123)I)-labelled VEGF(165) in patients with highly malignant osteosarcoma. METHODS: Two patients (a 15-year-old female and a 14-year-old male) with osteosarcoma were injected with 140 MBq [<130 pmol (<5 µg) VEGF(165) per patient] of (123)I-VEGF(165). Dynamic acquisition was initiated immediately after administration and carried out until 30 min after injection. Whole-body images were done in anterior and posterior views at various time points. All patients underwent single-photon emission tomography imaging. RESULTS: (123)I-VEGF(165) scans were positive in these patients. Sequential images clearly showed increased (123)I-VEGF(165) activity in osteosarcoma lesions. The tumour lesions were still visualized in whole-body images and single-photon emission tomography examinations 2 h after injection. Intravenous injection of (123)I-VEGF(165) did not cause any side effects. CONCLUSION: Our results suggest that (123)I-VEGF(165) receptor scintigraphy may be useful for the visualization of highly malignant osteosarcoma and/or metastasis and the angiogenic activity of the tumour.

The influence of tumor- and treatment-related factors on the development of local recurrence in osteosarcoma after adequate surgery. An analysis of 1355 patients treated on neoadjuvant Cooperative Osteosarcoma Study Group protocols.

BACKGROUND: Local recurrence (LR) in osteosarcoma is associated with very poor prognosis. We sought to evaluate which factors correlate with LR in patients who achieved complete surgical remission with adequate margins. PATIENTS AND METHODS: We analyzed 1355 patients with previously untreated high-grade central osteosarcoma of the extremities, the shoulder and the pelvis registered in neoadjuvant Cooperative Osteosarcoma Study Group trials between 1986 and 2005. Seventy-six patients developed LR. RESULTS: Median follow-up was 5.56 years. No participation in a study, pelvic tumor site, limb-sparing surgery, soft tissue infiltration beyond the periosteum, poor response to neoadjuvant chemotherapy, failure to complete the planned chemotherapy protocol and biopsy at a center other than the one performing the tumor resection were significantly associated with a higher LR rate. No differences were found for varying surgical margin widths. Surgical treatment at centers with small patient volume and additional surgery in the primary tumor area, other than biopsy and tumor resection, were significantly associated with a higher rate of ablative surgery. CONCLUSIONS: Patient enrollment in clinical trials and performing the biopsy at experienced institutions capable of undertaking the tumor resection without compromising the oncological and functional outcome should be pursued in the future.

[Modular tumor prostheses of the humerus]. / Modulare Tumorprothesen des Humerus.

The humerus is a common location of musculoskeletal tumors. Modular prostheses of the humerus, besides APC and biological reconstructions, allow restoration of resulting bone defects. The functional outcome is determined by the extent of bone and soft tissue loss. Anatomical shoulder prostheses have a limited abductor function, while shoulder function could be improved by an inverse prosthetic design and implants for ligament repair. Elbow prostheses provide satisfactory function. Our own results in 101 patients showed a 23% revision rate. The median overall survival was 171 months with an overall 5-year survival of 53%. With respect to good oncological outcomes modular reconstruction of the humerus is a feasible treatment option for cancer patients.

[Upper-extremity amputation in tumours of the shoulder and upper arm--experiences of the Vienna Bone Tumour Registry]. / Die Amputation an der oberen Extremität bei Tumoren der Schulter und des Oberarmes--Erfahrungen aus dem Wiener Knochengeschwulstregister.

Malignant lesions of the bones and soft tissues require radical or wide resection to achieve adequate therapy. Due to the many developments in terms of adjuvant modalities, diagnostics and surgical expertise today there are several modes of therapy as alternatives to amputation in the treatment of malignant tumours of the shoulder and upper arm. After resection of smaller tumours excellent functional results can be obtained by the use of modular endoprostheses, whereas large neoplasms adjacent to the neurovascular bundle require resection-replantation to allow salvage of the hand. Within the Vienna Bone Tumour Registry, 100 patients out of a total of more than 6500 have been treated for such lesions: 62 received an endoprostheses, 18 resection-replantation and 20 amputation. In cases of primary malignant tumours the incidence of lung metastases was higher in the resection-replantation group (50 %) and amputation group (42 %) than in the prostheses group (11 %), which has been linked to larger tumour size in the former two groups. Radical or wide resections were obtained in 95 % of the prostheses group, as compared to 75 % and 78 % in the amputation group and the resection-replantation group, respectively, due to invasion into the neurovascular bundle. Over time the number of amputations decreased simultaneously with the increase of endoprostheses whereas the number of resection-replantations remained equal at our institution. Amputation today still plays a crucial role in the treatment of intralesionally resected tumours, as surgical contamination can make limb salvage impossible. Therefore, the importance of biopsy in the therapeutical algorithm of bone and soft tissue tumours has to be emphasised again.

Pelvic reconstruction following resection of malignant bone tumours using a stemmed acetabular pedestal cup.

AIMS: Pelvic reconstruction after the resection of a tumour around the acetabulum is a challenging procedure due to the complex anatomy and biomechanics. Several pelvic endoprostheses have been introduced, but the rates of complication remain high. Our aim was to review the use of a stemmed acetabular pedestal cup in the management of these patients. PATIENTS AND METHODS: The study involved 48 patients who underwent periacetabular reconstruction using a stemmed pedestal cup (Schoellner cup; Zimmer Biomet Inc., Warsaw, Indiana) between 2000 and 2013. The indications for treatment included a primary bone tumour in 27 patients and metastatic disease in 21 patients. The mean age of the patients at the time of surgery was 52 years (16 to 83). RESULTS: At a median follow-up of 6.6 years (95% confidence interval 4.6 to 8.2), local control was achieved in all patients; 19 patients had died (16 of disease). Complications occurred in 19 patients (40%), of which deep infection was the most common, affecting eight patients (17%). Seven patients (15%) had a dislocation of the hip. Aseptic loosening was found in three patients (6%). Two (4%) underwent hindquarter amputation for non-oncological reasons. The risk of revision, with death being treated as a competing event, was 28% at one year, 39% at five years and 48% at ten years post-operatively. The mean Musculoskeletal Tumour Society Score at final follow-up was 71% (27% to 93%). CONCLUSION: This type of reconstruction is a satisfactory option for the treatment of patients with a periacetabular tumour. There remains, however, a high rate of complication, which may be reduced by future modifications of the device such as silver coating and tripolar articulation. Cite this article: Bone Joint J 2017;99-B:841-8.

Review of the outcomes of complex acetabular reconstructions using a stemmed acetabular pedestal component.

AIM: Until now, there has been no consensus as to whether stemmed acetabular components are appropriate for use in patients undergoing revision total hip arthroplasty (THA) who have major acetabular defects or pelvic discontinuity. We wished to address this deficiency in the literature. PATIENTS AND METHODS: We carried out a retrospective study of 35 patients (six men and 29 women) with a mean age of 68 years (37 to 87), with major acetabular defects who underwent revision THA between 2000 and 2012. RESULTS: At a mean follow-up of 63 months (24 to 141), a total of 15 patients (43%) had required at least one further operation. Six implants (17%) loosened aseptically, four (11%) were further revised for infection and two (6%) for technical failure. By taking revision for any reason as the endpoint, the rate of survival of the implant was 61% after five years; by taking revision for aseptic loosening as the end point, it was 78%. The cumulative five-year survival for aseptic loosening was 94% in patients without pelvic discontinuity, and 56% in those with pelvic discontinuity. CONCLUSION: These results indicate a significantly worse survival in patients with pelvic discontinuity (p = 0.020) and we advise caution in the use of the pedestal component in patients with major acetabular defects and pelvic discontinuity who require revision THA. As a result of these findings we have stopped using this implant and prefer to use particulate bone grafts protected with an anti-protrusion cage and posterior column plate fixation, if necessary. TAKE HOME MESSAGE: Based on these poor results, we advise caution if using the pedestal component in patients with major acetabular defects with the presence of a pelvic discontinuity. Cite this article: Bone Joint J 2016;98-B:772-9.

Osteosarcoma over the age of forty.

The European Musculo Skeletal Oncology Society (EMSOS) has carried out a retrospective review of patients over the age of 40 years with osteosarcoma. 481 patients from 12 centres or multicentric groups were included. 42 patients had osteosarcoma arising in Paget's disease, median survival was 9 months. Patients with axial or metastatic tumours also did badly whilst 41 patients with radiation-induced osteosarcoma had a prognosis paralleling conventional osteosarcoma matched for patient age and site of the tumour. 238 patients had high grade non-metastatic osteosarcoma and had a survival of 46% at 5 years. Older patients had less chemotherapy and fared worse. Osteosarcoma in the elderly is a curable condition and warrants intensive treatment with chemotherapy and surgical resection.

Recurrence of curetted and bone-grafted giant-cell tumours with and without adjuvant phenol therapy.

AIMS: Giant-cell tumour of bone (GCT) represents 5% of all primary bone tumours. The aim of this study was to compare the outcome of GCT treated with or without phenol. METHODS: Out of 53 patients primarily treated for a giant-cell tumour, 47 were followed, with a median follow-up of 11 (range 4-43) years. All patients were disease-free at the latest follow-up. Of the 40 tumours (85%) located in long bones, 14 (35%) were treated by curettage and bone grafting and 12 (30%) by additional adjuvant phenol treatment. Fourteen patients (35%) received different therapies, including en-bloc resection, endoprosthesis, cement packing or other therapy. RESULTS: There were seven (17.5%) recurrences in long bones after a median of 12 (range 4-60) months, three (3/14, 21%) in the group treated without phenol and three (3/12, 25%) in the group with phenol. Of the seven tumours located in the axial skeleton, two patients died within the first year after surgery. The remaining five patients were followed, with a median follow-up of 12 (range 8-23) years. No patients had metastases or a multicentric tumour. CONCLUSIONS: Despite the different rates of recurrence reported in literature, this study suggests that local recurrence rate of giant-cell tumours located in long bones treated with or without phenol is similar. Adequate removal of the tumour seems to be a more important predictive factor for the outcome of surgery than the use of phenol as an adjuvant therapy.

A long-term review of the treatment of patients with Ewing's sarcoma in one institution.

AIMS: The treatment of patients suffering from Ewing's sarcoma has changed over the last three decades. We report the analyses, significant prognostic factors, interdisciplinary approach and development of therapy in one institution in Austria. METHODS: One hundred and forty-two patients treated for Ewing's sarcoma between 1949 and 1994 were reviewed. Median follow-up was 8.5 years. Fifty-six patients were treated between 1949 and 1980 (group 1), and 86 patients between 1981 and 1994 (group 2). Patients in group 1 were treated with polychemotherapy. Patients in group 2 were treated with a neoadjuvant CESS (Cooperative Ewing's Sarcoma Study) regimen. In group 1, 24 patients underwent biopsy only, 32 patients had a definitive operation, 48 patients received either radiation therapy only or additional radiation therapy compared with in group 2: 6, 80 and 44 cases, respectively. RESULTS: Five-year overall survival (OS) increased from 27% to 57%. Significant prognostic factors for OS were pre-operative metastases (P=0.0001), tumour location (P=0.0048), type of chemotherapy (P=0.002) and response to chemotherapy (P=0.0004). Chemotherapy (P=0.037), tumour location (P=0.0017) and metastases at diagnosis (P=0.0025) were significant. CONCLUSION: The most effective treatment of Ewing's sarcoma is chemotherapy.

Chronic lower back pain due to sarcoma.

We describe a 74-year-old woman with extensive pelvic leiomyosarcoma presenting with uncharacteristic musculoskeletal pain of the lumbosacral region and left lower extremity. Hemipelvectomy was considered the treatment of choice, and a model for a pelvic prosthesis was constructed based on imaging analysis. However, the tumour (and the complaints) responded surprisingly well to a combined treatment regimen including superselective arterial catheter embolization, which led to tumour regression to such a degree that aggressive surgical treatment became unnecessary.

Peripheral osteoid osteoma. Is there still a place for traditional surgery?

We treated 106 patients with a peripheral osteoid osteoma by conventional surgical methods; 81 had curettage and 25 en-bloc resection. The rate of local recurrence after curettage was 12% and after en-bloc resection 4.5%. Postoperative fractures were observed in 3% after curettage and in 4.5% after en-bloc resection. We compared our findings with those reported in the literature after minimally invasive treatment and concluded that curettage can be regarded as the treatment of choice in patients in whom minimally invasive methods do not offer any advantage, for example, for subperiosteal tumours which are readily accessible, or when the diagnosis is unclear and further histological analysis is required.

Revision of the Kotz type of tumour endoprosthesis for the lower limb.

In 251 patients over a period of 15 years an uncemented Kotz modular femoral and tibial reconstruction mega prosthesis was implanted after resection of a malignant tumour of the lower limb. Twenty-one patients (8.4%) underwent revision for aseptic loosening, again using an uncemented prosthesis, and five of these required a further revision procedure. The median follow-up time from the first revision was 60 months (11 to 168) and after a second revision, 33 months (2 to 50). The probability of a patient avoiding aseptic loosening for ten years was 96% for a proximal femoral, 76% for a distal femoral and 85% for a proximal tibial implant. At the time of follow-up all radiographs were assessed according to the International Symposium of Limb Salvage criteria. The first radiological signs of aseptic loosening were always seen at the most proximal or distal part of the anchorage stem at a mean of 12 months (4 to 23) after the first implantation. Using the Musculoskeletal Tumor Society score for evaluation, the clinical results showed a mean of 88% of normal function.

Bone mineral density in long-term survivors of highly malignant osteosarcoma.

We studied the bone mineral density (BMD) of 48 long-term survivors of highly malignant osteosarcoma who had been treated according to the chemotherapy protocols of the German- Swiss-Austrian Co-operative Osteosarcoma Study Group which include high-dose methotrexate. The mean age of the patients was 31 +/- 4.2 years and the mean follow-up 16 +/- 2.2 years. The BMD of the lumbar spine and of the proximal femur of the non-operated side was measured by dual-energy x-ray absorptiometry. A questionnaire was given to determine life-style factors, medical history and medication. Ten patients were osteoporotic, 21 osteopenic and 17 normal according to the WHO definition. Eighteen patients suffered fractures after receiving chemotherapy and all had significantly lower levels of BMD for all the sites measured.

[Analysis of the migration of cementless all-metal hip endoprosthesis]. / Migrationsanalyse von zementfreien Ganzmetall-Hüfttotalendoprothesen.

Since September 1997, 58 patients have received a newly developed all-metal hip prosthesis at the department of orthopaedic surgery, University Hospital Vienna. In a retrospective study, the migration profile of 26 acetabular components of these prostheses with all-metal cups was evaluated. A total of 25 patients (10 men, 15 women, mean age 61 years) who had been operated on earlier than 11 months previously were studied. Indications included coxarthrosis (15), congenital dysplasia of the hip (7), post-traumatic coxarthrosis (3), and change of the implant due to infection (1). Twenty-three patients (7 men, 16 women; mean age 63 years) with 25 metal-backed polyethylene implants and matched demographic data, indications and cup size, served as the group for comparison. The mean duration of follow-up for both groups was 14 months. For analysis of migration a modified version of Dickob's method for digital measurement of comparative hip radiographs was used. Measurements were performed three times by one examiner. Migration values of more than 2.0 mm were regarded as a sign of possible cup loosening. After 13 to 20 months the average migration was -0.10 mm in horizontal and 0.18 mm in vertical direction for all-metal prostheses, and -0.20 mm horizontally and 0.47 mm vertically for the other group. Mean migration values exceeded the critical limit of 2.0 mm in two patients in the all-metal group, one of whom also had clinical signs of cup loosening. The covariance analysis of the highest migration levels of each patient revealed no significant differences between the groups; the postoperative Harris hip score was 98 points (range, 93-100) in the all-metal group and 97 (range, 92-100) in the other. Provided metal is carefully processed and cups are initially stable, the all-metal implants have equivalent in-growth as expressed by the migration analysis, and thus constitute an alternative therapeutic modality without polyethylene components.

[Growing prostheses for reconstruction of lower limb defects in children]. / Wachstumsprothesen zur Rekonstruktion von Defekten der unteren Extremitäten beim Kind.

OBJECTIVE: Bone defect reconstruction with growing prostheses after resection of malignant bone tumors using the technique of extendable prostheses. INDICATIONS: Limb salvage surgery after resection of primary malignant bone tumors in the growing skeleton for expected leg length deficiencies > 4 cm. CONTRAINDICATIONS: Palliative tumor resection, infection, systemic metastases at the time of diagnosis, social contraindications, lack of compliance of the patient and/or family. SURGICAL TECHNIQUE: Wide resection of the tumor with resection of the biopsy location. Reconstruction with the growing prosthesis. Planned lengthening operations. POSTOPERATIVE MANAGEMENT: Mobilization with crutches, weight bearing or partial weight bearing according the prosthesis' fixation. Chemotherapy as defined in the chemotherapy protocol. Planned minimally invasive lengthening or noninvasive lengthening according to the type of growing module. RESULTS: Since 1969, more than 8,632 patients have been registered in the Vienna Bone and Soft Tissue Tumor Registry. Of these, 691 patients suffered from osteosarcoma and 243 from Ewing's sarcoma. A total of 513 patients were < 18 years of age (54.4%). Since 1987, 71 patients have been treated with growing prostheses: 13 patients died of disease, and 44 patients reached maturity. The overall 5- and 10-year survival were 84% and 77%, respectively. The patient group consisted of 26 girls and 18 boys, mean age at surgery 10 ± 3 years. The diagnosis was 34 osteosarcoma and 10 Ewing's tumors. The patients had a mean of 4 ± 3 elongation procedures to reach an elongation of 72.5 ± 53.45 mm. The average elongation per procedure was 14.83 ± 4.6 mm.

Tumor-induced hypophosphatemic rickets in an adolescent boy--clinical presentation, diagnosis, and histological findings in growth plate and muscle tissue.

CONTEXT: The mechanism behind disabling muscle weakness in tumor-induced hypophosphatemic rickets is obscure. Histological investigation of growth plate tissue of patients with tumor-induced osteomalacia has so far not been reported. PATIENT: A mesenchymal tumor was detected in the left distal fibula by (68)Ga-DOTATOC in a 17-yr-old boy with adolescent onset of severe hypophosphatemic rickets. Disabling muscle weakness improved within days after surgery, and normal mobility was restored within months. METHODS AND RESULTS: The resected tissue included part of the growth plate allowing immunohistochemical investigation. Positive staining of FGF23 was found in the tumor cells and in hypertrophic chondrocytes, osteoblasts, and osteoclasts of the adjacent growth plate. This distribution matched that found in growth plate tissue of a healthy control. We found positive staining for the somatostatin receptor not only in the tumor but also within the growth plate and adjacent bony tissue in the patient and the healthy control. Muscle tissue provided evidence for a partial defect in respiratory chain complexes I-IV. Biochemical markers were nearly or completely restored to normal 12 months after surgery. CONCLUSIONS: Hypertrophic growth plate chondrocytes are a target or source of FGF23 in tumor-induced osteomalacia. Low serum phosphate, FGF23, or other factors produced by the tumor may interfere with mitochondrial function.