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Purpose Patella maltracking is among the most frequent causes of poor outcomes and early failure after total knee arthroplasty (TKA), with an incidence that ranges from 1 to 20%. Even if there is agreement between authors regarding the preoperative and intraoperative management of patella maltracking in TKA, less clear are postoperative conducts. The purpose of this systematic review is to summarize and compare surgical techniques used to treat patella maltracking after TKA. Methods A systematic review of the literature was performed with a primary search on Medline through PubMed. The PRISMA 2009 flowchart and checklist were used to edit the review. Screened studies had to provide clinical, functional and radiological results and complications of the proposed treatment to be included in the review. Results A total of 21 articles were finally included. Three main types of surgical procedures and other minor techniques have been identified to manage patella maltracking after TKA. The choice of the proper technique to use in the specific case depends on several factors, first of all the malpositioning of the prosthetic components. Conclusion Patella maltracking after TKA represents a frequent and challenging problem for orthopedic surgeons. Treatments described in the literature are often able to correct an abnormal patellar tracking; nevertheless, authors report variable percentages of residual knee pain and dissatisfaction in re-treated patients. Therefore, it would be desirable to prevent the maltracking condition at the time of primary arthroplasty, using proper surgical precautions.

Purpose Total knee replacement (TKR) failure represents a hard challenge for knee surgeons. TKR failure can be managed in revision with different constraint, related with soft and bone knee damages. The choice of the right constraint for every failure cause represents a not summarized entity. The purpose of this study is identifying distribution of different constraints in revision TKR (rTKR) for failure cause and the overall survival. Methods A registry study based on the Emilia Romagna Register of the Orthopaedic Prosthetic Implants (called RIPO) was performed with a selection of 1432 implants, in the period between 2000 and 2019. Selection implants including primary surgery constraint, failure cause and constraint revision for every patient, and divided for constraint degrees used during procedures (Cruciate Retaining-CR, Posterior Stabilized-PS, Condylar Constrained Knee-CCK, Hinged). Results The most common cause of primary TKR failure was aseptic loosening (51,45%), followed by septic loosening (29,12%). Each type of failure was managed with different constraint, the most used was CCK in the most of failure causes, such as to manage aseptic and septic loosening in CR and PS failure. Overall survival of TKA revisions has been calculated at 5 and 10 years for each constraint, with a range of 75.1–90.0% at 5 years and 75.1–87.5% at 10 years. Conclusion Constraint degree in rTKR is typically higher than primary, CCK is the most used constraint in revision surgery with an overall survival of 87.5% at 10 years.

The aim of the present study is to evaluate the results of our all posterior-one stage surgical technique for the reduction and fusion of high-grade high-dysplastic spondylolisthesis.Patients over 11 years old with high-grade spondylolisthesis treated by reduction and circumferential fusion with a posterior-only approach were reviewed. Data about operative time, blood loss, length of stay, intra- and postoperative complications were collected. Meyerding grade (M), lumbar lordosis (LL), thoracic kyphosis (TK), pelvic incidence (PI), pelvic tilt (PT), lumbosacral angle (LSA), slip angle (SLIP), lumbar index (LI) and severity index were measured on preoperative and last follow-up. Sagittal vertical axis (SVA) was used to assess sagittal balance.Of the 14 included patients, L5-S1 arthrodesis was performed in 12 cases, and L4-S1 was performed in 2 cases. Average surgical time was 275 ± 65 min; average blood loss was 635 ± 375 mL. Average length of stay of was 3.9 ± 1.5 days. The SLIP angle improves from 33.8° ± 7.3° to 6.4° ± 2.5°, (p = 0.002); the lumbosacral angle improves from 68.8° ± 18.6° to 100.7° ± 13.2°, (p = 0.01); and the SVA decreased from 49.4 ± 22.1 mm to 34.4 ± 8.6 mm (p = 0.02). No significant changes were observed in PI, PT and SS. Thoracic kyphosis (TK) and lumbar lordosis (LL) did not change significantly. At last follow-up, no patient had surgical site infection or mechanical complications; no pseudoarthrosis was observed. No revision surgery was performed.Although technically demanding, reduction and fusion with one stage all posterior approach prove to be a safe and effective.

Pedicle screws is the current gold standard in spine surgery, achieving a solid tricolumnar fixation which is unreachable by wires and hooks. The freehand technique is the most widely adopted for pedicle screws placing. While freehand technique has been classically performed with manual tools, there has been a recent trend toward the use of power tools. However, placing a pedicle screw remains a technically demanding procedure with significant risk of complications. The aim of this article is to retrospectively evaluate safety and accuracy of free-hand power-assisted pedicle screw placement in a cohort of patients who underwent correction and fusion surgery for scoliosis (both idiopathic and non-idiopathic) in our department. A retrospective review of all patients with scoliosis who underwent surgery and received a postoperative CT scan in our department in a 9-year period was undertaken. Screw density, number and location of pedicle screws were measured using pre and postoperative full-length standing and lateral supine side-bending radiographs. Then, postoperative CT scan was used to assess the accuracy of screw placement according to Gertzbein-Robbins scale. Malpositioned screws were divided according to their displacement direction. Finally, intra and postoperative neurological complications and the need for revision of misplaced screws were recorded. A total of 205 patients were included, with a follow-up of 64.9 ± 38.67 months. All constructs were high density (average density 1.97 ± 0.04), and the average number of fusion levels was 13.72 ± 1.97. A total of 5522 screws were placed: 5308 (96.12%) were grade A, 141 (2.5%) grade B, 73 (1.32%) grade C. Neither grade D nor grade E trajectories were found. The absolute accuracy (grade A) rate was 96.12% (5308/5522) and the effective accuracy (within the safe zone, grade A + B) was 98.6% (5449/5522). Of the 73 misplaced screws (grade C), 59 were lateral (80.80%), 8 anterior (10.95%) and 6 medial (8.22%); 58 were in convexity, while 15 were in concavity (the difference was not statistically significant, p = 0.33). Intraoperatively, neither neurological nor vascular complications were recorded. Postoperatively, 4 screws needed revision (0.072% of the total): Power-assisted pedicle screw placing may be a safe an accurate technique in the scoliosis surgery, both of idiopathic and non-idiopathic etiology. Further, and higher quality, research is necessary in order to better assess the results of this relatively emerging technique.

Several surgical procedures have been described to treat hallux rigidus. Keller arthroplasty is a joint-sacrificing procedure proposed in 1904. Considering the current trends to mini-invasiveness and the debate about the technique's suitability, this review intends to state Keller arthroplasty results and the conditions where it could be still adopted in the treatment of hallux rigidus.Selected articles were reviewed to extract: population data, surgical indications, different surgical techniques, clinical and radiological outcomes, and complications.Seventeen retrospective studies were selected, counting 508 patients. Mean age at surgery was 55 years. Patients were affected by moderate-severe hallux rigidus. Three modified Keller arthroplasty were identified. Good clinical and radiological outcomes were reported. Metatarsalgia was the most frequent complication (12%).Despite for many authors KA seems a viable surgical treatment for middle aged and elderly patients affected by moderate-severe hallux rigidus, the available literature provides little evidence on the real efficacy and safety of the technique. A non-negligible percentage of complications may occur, and therefore is essential to set correct indications through an accurate patients' selection.

Little evidences are available in the literature concerning the outcomes of total knee replacement (TKR) in poliomyelitis patients with severe knee deformities or degeneration. Encouraging results have been reported concerning the use of constrained implants, i.e., rotating hinge knee prosthesis (RHK), compared to less constrained ones. The purpose of this paper is to report our experience with rotating hinge total knee replacement, using only RHK prosthesis, to determine functional results, complications, and survival of TKR in poliomyelitis patients. We performed a retrospective chart review of 14 patients with a history of knee osteoarthritis following poliomyelitis that underwent primary TKR, for a total of 15 surgical procedure (one bilateral case). Preoperative and postoperative clinical measurements have been conducted for all patients using the Knee Society Score (KSS). Hip-knee angle, recurvatum knee angle, and Insall-Salvati index were evaluated with full weight-bearing panoramic view X-ray preoperatively and postoperatively. The 2-year postoperative clinical KSS significantly improved from the preoperative scores. The average clinical KSS improved from 32,9 (range 3–48) preoperatively to 77,4 (range 60–88) postoperatively (P value P value

OBJECTIVE: We performed a systematic review of surgical treatment of the infected total ankle arthroplasty. The purpose of this investigation was to describe the current trends and to perform a critical analysis of the evidence reported in the existing literature. MATERIALS AND METHODS: A comprehensive search for all relevant articles published in English was conducted. Scientific databases were accessed to identify papers dealing with the management of the infected total ankle arthroplasty. We identified and collected every patient that underwent a surgical management of infected ankle arthroplasty. Data extracted were summarized and reported. A descriptive analysis was performed; when possible, a statistical analysis was accomplished. RESULTS: Thirty-two papers (152 infected ankle arthroplasty) published in the last 20 years were identified. Twenty-seven patients (17.76%) were treated with irrigation and debridement, revision total ankle arthroplasty was performed in 72 cases (47.37%), arthrodesis was performed as a primary treatment in 30 patients (19.74%), 12 patients (7.89%) underwent a spacer arthroplasty while amputation was performed as a primary treatment in 9 patients (5.92%). CONCLUSIONS: Our study reveals the improvement of the surgical management of the infected total ankle arthroplasty through the last 20 years. Irrigation and debridement and two-stage revision represent the most viable treatment in acute postoperative and late chronic infections respectively. We noted a trend towards maintaining articularity through a two-stage revision. The quality of evidence is weak with biases both in reporting and selection process. High quality randomized controlled trials are required to compare different treatments in order to introduce an evidence-based treatment protocol.

Introduction: Carpal tunnel syndrome (CTS) in children represents a complex challenge for the hand surgeon because of its rarity, poor patient cooperation, frequently associated malformation syndromes and mental retard, atypical symptoms and nuanced and poor sensitivity of instrumental tests. The most frequently associated causes with the CTS in children are rare congenital malformations and diseases, requiring an overall assessment of the young patient and a high degree of suspicion for the potentially associated canalicular syndrome. On the other hand, the associated syndromes may be the main ally for a diagnosis that starts from the knowledge of the literature and the surgeon's suspicion by observing the child wailing. Early diagnosis and decompression treatment is mandatory. Materials and methods: The authors report a case series of 26 children and analyze the etiology and diagnostic algorithms. Patient assessment was based on complete clinical examination and medical history collection of these young patients with the involvement of the family and educators. Results: In all 26 patients treated, along an average period of 23 months (minimum 12, maximum 30), no signs of recurrence or persistence of median nerve disturbances were recorded. Conclusions: In conclusion, we believe that anamnesis, a careful physical examination and analysis of instrumental examinations, should be accompanied by a thorough knowledge of rare diseases in the context of congenital malformations. The carpal tunnel syndrome, while well known and treated by each orthopedic surgeon, reveals a mysterious aspect in the context of the "fabulous" world of childhood illnesses, even more difficult than rare congenital diseases.

Bone response to hydroxyapatite coating on stainless steel has not been so extensively tested in animals as it happened for other metallic substrate, like Ti6Al4V. For this reason, authors performed an in vivo histomorphological electron microscopic study of hydroxyapatite coating on duplex stainless steel cylinders, to gather further evidences on the characters of bone apposition at the interface. Sixteen HA-coated cylinders were implanted in the distal femur of New Zealand White rabbits. Comparison with uncoated controls was made. Retrieval steps were at: 4, 8, 26 and 34 weeks. Specimens were analyzed in a Jeol JSM 6301F scanning electron microscope. The response to HA-coated samples has a morphological character of tight apposition between bone and coating. Osteocytic lacunae may be found few microns close to the coating and newly formed bone is extremely interlocked with it so that even an higher magnification electron-microscopy cannot resolve any discontinuity in between. Pictures of physiological bone-turnover are distinguishable at the bone-coating interface; areas of well preserved coating may be present together with areas where local exfoliation or fragmentation has already completely exposed the metallic substrate. On the opposite in uncoated samples, despite a morphological picture of properly formed bone, the largest area of the metal has no direct apposition with it.

Intraoperative femoral fractures are a serious complication of total hip replacement. The purpose of this study was to evaluate the risk factors of intraoperative femoral fractures in a retrospective analysis of a series of 3,566 total hip replacements.The patients were divided into two groups, A and B. Group A patients had no intraoperative femoral fractures and Group B patients had intraoperative femoral fractures. In Group A there were 3,483 patients (97.7%) and in Group B, 83 (2.3%). The following potential risk factors were evaluated: sex, age, diagnosis, previous surgery at the homolateral hip, surgical approach, fixation type of the femoral component, prosthesis type, surgical stage during which the fracture occurred, and the lead operating surgeon.The fracture incidence was higher in females (p0.005) in uncemented femoral components (p = 0.005), in patients who had previous surgery at the homolateral hip (p0.005), and in revision surgery (p0.005).The analysis of intraoperative femoral fracture risk factors should allow the surgeon to improve the surgical performance and therefore reduce the incidence of this severe intraoperative complication.

The purpose of this paper is to evaluate in an animal model the long term results obtained with a prosthetic stem fully coated with hydroxyapatite. The cup was manufactured in polyethylene and was cemented. Six arthroplasties were performed in six sheep. After twelve months, the animals were euthanized and the femurs were harvested and processed for undecalcified sectioning. Twelve cross sections were cut perpendicularly to the longitudinal stem axis. Sections one to five corresponded to the area of the stem which, at the time of surgery, had a full initial contact between the bone and the prosthesis; sections six to ten corresponded to the area of the stem which, at the time of surgery, had a gap from 0 to 2 mm between the bone and the prosthesis; sections eleven and twelve had an initial gap larger than 2 mm. At one year after implantation, in the sections one to five, morphological analyses showed extensive direct contact between the bone and the hydroxyapatite coating. Bone prosthesis contact was lower in the sections six to ten. No contact was seen in sections eleven and twelve. Comparing bone to prosthesis contact of each subsequent section, from proximal to distal, the difference becomes significant with section five compared to section six (p0.00005). No detachment of the hydroxyapatite coating from the metallic substrate was observed in any section. In conclusion, this study shows that a conic shaped femoral stem, fully coated with hydroxyapatite gives very good histological and histomorphometric results at one year. Prosthesis osteointegration showed to be influenced by the initial bone to prosthesis contact. No direct bone to prosthesis contact was achieved if the initial bone to prosthesis gap was larger than 2 mm.

Low-frequency pulsed electromagnetic fields (hereafter PEMFs) have now been in use in orthopaedics and traumatology for upwards of twenty years. The technique is employed to promote osteogenesis and hence to favour bone repair proc esses1–4. It has recently been shown that PEMFs may be the treatment of choice in avascular necrosis of the femoral head. The treatment has emerged as especially effective in the earliest forms in the staging according to Ficat5.

ùDynamic Hip Screw is wide3ly used to treat trochanteric fractures, althrought significant failure rates have been reported due to lag screw cut-out. This study was designed to compare tratment with DHS fixed with either standard or hydroxyapatite coated lag in cortical screw in elderly osteoporotic throcanteric fracture patients

Background: Although the use of a sliding hip screw is considered to be the preferred treatment for pertrochanteric femoral fractures, we theorized that external fixation could produce clinical outcomes equal to, if not better than, the outcomes obtained with conventional treatment. Furthermore, because external fixation is minimally invasive, we expected a lower rate of morbidity and a reduced need for blood transfusions. Therefore, we compared the two treatments in a clinical trial of elderly patients with pertrochanteric fracture. Methods: Forty consecutive elderly female patients who had a pertrochanteric fracture were randomized to be treated with either fixation with a 135° four-hole sliding hip screw (Group A) or an external fixation device with hydroxyapatite-coated pins (Group B). The inclusion criteria were female gender, an age of at least sixty-five years, an AO/OTA type-A1 or A2 fracture, and a bone mineral density T-score of less than -2.5. There were no differences in patient age, fracture type, bone mineral density, comorbidities, length of hospital stay, or quality of reduction between the two groups. Results: The average intraoperative time (and standard deviation) was 64 ± 6 minutes in Group A and 34 ± 5 minutes in Group B (p < 0.005). The average number of units of blood transfused postoperatively was 2.0 ± 0.1 in Group A and none in Group B (p < 0.0001). Group B had less pain five days postoperatively (p < 0.05). Varus collapse of the fracture at six months averaged 6° ± 8° in Group A and 2° ± 1° in Group B (p < 0.002). No pin-track infections occurred in Group B. The average Harris hip score at six months was 62 ± 19 points in Group A and 63 ± 17 points in Group B. Conclusions: This study showed that external fixation with hydroxyapatite-coated pins is an effective treatment for this fracture in this patient population. The operative time is brief, the blood loss is minimal, the fixation is adequate, and the reduction is maintained over time. Level of Evidence: Therapeutic Level I. See Instructions to Authors for a complete description of levels of evidence.

Sliding hip screw fixation is the most common surgical treatment for pertrochanteric fractures. Intramedullary hip screw fixation is another popular surgical option; however, for either sliding hip screw or intramedullary hip screw fixation, mechanical complications such as lag screw cut-out are frequent. Furthermore with these fixation techniques, the inability to restore previous hip anatomy is common. Recently, external fixation has been proposed as a suitable fixation technique for pertrochanteric fractures. The main advantages of external fixation include: minimally invasive, short operative time, limited blood loss, and maintenance of the reduction obtained at surgery. For these reasons, we evaluated the results of pertrochanteric fractures treated with external fixation after a minimum follow-up of 6 months. Ten consecutive female osteoporotic patients (age ≥ 65 years) with AO/OTA fracture type A 1 or A 2 were included in the study. Fractures were treated with Orthofix pertrochanteric fixator (OPF) with four hydroxyapatite (HA)-coated pins. The mean patient age was 82 ± 7 years. The mean operative time was 34 ± 5 min. Fixators were removed three months postoperatively. There was union in all fractures. No blood transfusions were required postoperatively. There was no pin-track infection. The mean pin-insertion torque was 1 962 ± 1 215 N/mm and the mean pin extraction torque was 2 784 ± 1 648 N/mm. These latter results indicated improved pin fixation over time (p < 0.0005). There was no significant change in fracture reduction over time since there were no differences between the femoral-neck-shaft angle at 6 months and postoperatively. This study demonstrates that external fixation is a reliable treatment option for osteoporotic pertrochanteric fractures.

Introduzione Lo scopo di questo lavoro è valutare comparativamente 2 gruppi di pazienti affetti da frattura di collo di femore Gardner tipo 1 e 2 trattati mediante osteosintesi con viti percutaneeestandard e viti rivestite di idrossiapatite. Metodo Sono stati selezionati 60 pazienti con frrattura di collo di femore Gardner tipo1 e 2, età >65 anni, grado di osteoporosi con DEXA

H ip fractures are the most severe of all fragility fractures. It has been calculated that more deaths are caused by hip fractures than by other common severe diseases such as cancer of the stomach or the pancreas1. Furthermore, regardless of the quality of surgical treatment, hip fractures remain a major cause of disability. The economic implications are clear. In the United States, hip fracture management already costs approximately $13.8 billion per year2. In Europe, the average acute hospital cost is approximately €25,000 per fracture and the total care cost is as much as 2.5 times higher3. Approximately 200,000 pertrochanteric fractures (AO/OTA fracture type A1 and A2) per annum occur in the United States alone4. It has been calculated by the United States Census Bureau that, by the year 2020, the average life expectancy will be eighty-two years for women and seventy-four years for men5. This longer life expectancy will be associated with a dramatic increase in the number of pertrochanteric fractures. The functional results of treatment of pertrochanteric fractures are often unsatisfactory. The mortality rate has been reported to be 18% in the first year following operative treatment6. The results are influenced by the inability of the implant to remain well fixed in osteoporotic bone during the time required for fracture-healing. Implant failure and loss of reduction, which often lead to fracture malunion, are frequent complications of osteoporotic pertrochanteric fractures. Because fracture stability is crucial for bone repair, poor bone quality remains a concern that must be given priority when the type of implant is being chosen7. The primary aim of surgical treatment is to obtain good fracture reduction and to maintain this reduction until sufficient stability is provided by the fracture callus. If stable …

Symptomatic tendon tears are one of the most important causes of pain and joint dysfunction. Among the intrinsic causes, vascularization recently gained a major role. Endothelial function is indeed a key factor, as well as vascular tone and thrombotic factors, in the regulation of vascular homeostasis and the composition of vascular wall. In this review, we studied systematically whether there is a relationship between endothelial dysfunction and tendinopathy. A literature search was performed using the isolated or combined keywords endothelial dysfunction and tendon,' 'nitric oxide (NO) and tendinopathy,' and 'endothelial dysfunction in tendon healing.' We identified 21 published studies. Of the selected studies, 9 were in vivo studies, 2 focusing on animals and 7 on humans, while 12 reported about in vitro evaluations, where 7 were carried out on humans and 5 on animals. The evidence about a direct relationship between tendinopathy and endothelial dysfunction is still poor. As recent studies have shown, there is no significant improvement in clinical and functional assessments after treatment with NO in patients suffering from tendinopathy in different locations. No significant differences were identified in the outcomes reported for experiment group when compared with controls treated with conventional surgical procedures or rehabilitation programs. Nitric oxide could be a marker to quantify the response of the endothelium to mechanical stress or hypoxia indicating the final balance between vasodilatating and vasoconstricting factors and their effects, but more ad stronger evidence is still needed to fully support this practice.

At present, a big effort of the scientific community has been directed toward a more proper and standardized approach to the patients affected by degenerative scoliosis, and recent attention has turned toward the development of classification schemes. A literature analysis highlighted several classification schemes developed for degenerative scoliosis patients: the Simmons classification system, the Aebi system, the Faldini working classification system, the Schwab system, and the Scoliosis Research Society system. Aim of the current manuscript is to scrutinize the available literature in order to provide a comprehensive overview of these current classification schemes for adult scoliosis, by describing and commenting clinical development, limits and potential of their application together with their implications for surgical planning.

Forearm nonunion frequently changes the relationship between the radius and ulna and may lead to impairment of forearm function. We propose a new surgical technique for aseptic forearm nonunions combining a fibular cortical autograft strut with a metal plate and a fibular intercalary autograft in cases with a segmental bone defect. We retrospectively reviewed 20 patients with a mean age of 31 years (range, 17–48 years) at the time of surgery. Minimum followup was 12 years (mean, 14 years; range, 12–21 years). There were no intraoperative or postoperative complications. At last followup, all forearm bones had remodeled. The mean visual analog pain scale was 1 (range, 0–3). Forearm function improved; there were no radiographic signs of ankle arthritis at followup. Surgical treatment of aseptic forearm nonunions by combining a massive fibular cortical autograft strut with a plate and associating a fibular intercalary autograft in case of a segmental bone defect led to bone healing, improved forearm function, and a durable outcome with long-term followup. Level of Evidence: Level IV, therapeutic study. See the Guidelines for Authors for a complete description of levels of evidence.

Degenerative spondylolisthesis is characterized by the slippage of one vertebral body over the one below, with association of intervertebral disc degeneration and degenerative arthritis of the facet joints, which cause spinal stenosis. The aim of this study was to evaluate the clinical and radiographic results of 22 patients with symptomatic degenerative spondylolisthesis, operated on by decompressive laminectomy and instrumented posterolateral fusion associated with interbody fusion (PLIF). Mean age at surgery was 64 years (range, 57–72). Clinical results were evaluated on a questionnaire at the last follow-up visit concerning postoperative low back and leg pain, restriction of daily life activities, and resumption of sports activity. Lumbar spine radiographs were used to evaluate the status of fixation devices, the reduction of the spondylolisthesis, the lumbar sagittal balance and the presence of spinal fusion. No intraoperative or postoperative complications were encountered. There were no superficial or deep infections, fixation device loosening, or hardware removal. Mean follow-up time was 4 years (range, 3–6 years). Clinical outcome was excellent or good in 19 patients and fair in 3 patients. Preoperatively, mean forward vertebral slipping on neutral lateral radiographs was 5 mm, while postoperatively it decreased to 3 mm. Preoperatively, mean sagittal motion was 3 mm and angular motion was 8°, while postoperatively these values decreased to 1 mm and 1°, respectively. This study demonstrated that spinal decompression followed by transpedicular instrumentation associated with PLIF technique is a valid surgical option for the treatment of degenerative spondylolisthesis with symptomatic spinal stenosis. Clinical outcome, intended as relief of pain and resumption of activity, was improved significantly and fusion rate was high.

Growth hormone (GH) is fundamental for the maintenance of bone mass and metabolism both during childhood and in adulthood. This effect is due to a complex interaction between circulating GH and IGF-I produced peripherally. In vitro data and experimental animal models have clarified many of the regulatory mechanisms underlying the characteristic skeletal changes occurring in acromegaly. This review focuses on the effects of GH excess on bone metabolism and mass in acromegalic patients and, in particular, on the influence of factors such as hypogonadism, gender, age and therapy on bone metabolism and arthropathy.