Stress Fracture of Proximal Femur after Hip Resurfacing Treated with Cannulated Screw.

Stress fractures of the proximal femur are described in athletes and military personnel. In most cases, they are not treated surgically, except when they are at the top of the femoral neck and with cortical involvement. The return to sports is not recommended in patients with hip replacement, especially for the high rate of revision of implants in the younger patients. One of the major complications of hip resurfacing (HR) is the medial fracture of the femoral neck, which usually occurs within 9 weeks after surgery. The causes have to be attributed to a malposition of the femoral component or to an insufficient bone density. The case reported herein is unique because it describes a stress fracture on patient operated with HR, treated with screw fixation. Two years after surgery, the patient returned to his normal life, practicing sports, without progression of varus angulation of the stem.

Clinical and radiographic outcomes of the Birmingham Hip Resurfacing arthroplasty at a minimum follow-up of 10 years: results from an independent centre.

BACKGROUND: Metal-on-metal hip resurfacing (MoMHR) has been proposed as an effective surgical treatment for young and active patients with symptomatic hip disease. Recently, good clinical and radiographic outcomes have been reported by the designer surgeons at a 15.3 years follow-up; however, results at long follow-up by non-designer surgeons are less satisfactory. The aim of the study was to investigate if MoMHR can produce satisfactory clinical and radiographic results and if survival rate can be high even if the procedure is performed by non-designer surgeons. METHODS: All patients were assessed about implant survival. All patients completed an Oxford Hip Score (OHS), Harris Hip Score (HHS) and a University of California Los Angeles (UCLA) activity score preoperatively, at 1 year and at last available follow-up; at this time, a standard anteroposterior weight-bearing radiograph was performed. RESULTS: The survival rate with revision for any reason is 96%, similar to those obtained by designer surgeons. All the clinical scores improved over time: according to the OHS the survivors are asymptomatic and according to the UCLA maintain a high level of function. 6 remodellings of the femoral neck and 2 heterotopic bone formations were seen, but they were asymptomatic. CONCLUSIONS: As designer surgeons have already shown, MoMHR can provide in active patients a durable treatment for hip arthritis, with low risk of revision and good results at 10 years follow-up, even if the procedure is performed by non-designer surgeons.

Surgical treatment and management of hip fracture patients.

INTRODUCTION: Osteoporosis-related hip fractures are associated with high mortality and costs. The optimum type of treatment for such fractures is controversial. To shed some light on this issue, the surgical treatment and management of osteoporotic hip fractures were discussed during a hip fracture surgical working group at the 2009 International Society For Fracture Repair Annual Meeting comprising leading experts in the field. MATERIALS AND METHODS: The working group consisted of eight orthopaedic surgeons, six industry representatives and one research scientist. Eleven participants were from Europe and four were from the USA and Canada. Two chairmen posed 12 questions relating to the surgical treatment and management of osteoporotic hip fractures. Each question was discussed and key points were noted. RESULTS: Surgery should commence within 24-48 h but the patient should be optimized if presenting with ≥3 comorbidities. Specialized centres integrating orthopaedics, geriatricians and rheumatologists could be a solution for the lack of specialist care post-surgery. Surgical technique is important in fracture fixation, as is the implant, but there has been no improvement in implant design in the past 50 years. As a consequence, malunion has become unjustifiably accepted. Fracture healing can be accelerated using pharmaceuticals which are also important in secondary prophylaxis. All displaced femoral neck fractures in geriatric patients should be treated with hip replacement, the choice between using cemented or uncemented fixation being at the surgeon's discretion. DISCUSSION AND CONCLUSION: This working group discussion highlighted several important issues which could be of interest to the orthopaedic community.

Cushion bearings versus large diameter head metal-on-metal bearings in total hip arthroplasty: a short-term metal ion study.

INTRODUCTION: Metal-on-metal total hip arthroplasty (MOM THA) has the advantage of replicating the femoral head size, but the postoperative elevation of serum metal ion levels is a cause for concern. Metal-on-polycarbonate-urethane is a new cushion bearing featuring a large diameter metal head coupled with a polycarbonate-urethane liner. AIM: The aim of this study was to assess and compare serum cobalt (Co) and chromium (Cr) levels in a group of 15 patients treated with a cushion bearing THA system (Group A) and a group of 15 patients treated with a MOM THA system (Group B) at short-term. At a mean follow-up of 27.3 months (18-35 months), in Group A the median Cr and Co serum levels were significantly lower than in Group B, measuring 0.24 µg/L (0.1-2.1 µg/L) and 0.6 µg/L (0.29-2.3 µg/L) compared to 1.3 µg/L (0.1-9 µg/L, p < 0.001) and 2.9 µg/L (0.85-13.8 µg/L, p < 0.001) respectively. RESULTS: All patients demonstrated an excellent clinical result, as shown by the Harris and Oxford hip scores. The cushion bearing THA studied in this paper showed clinical outcomes similar to the MOM THA bearing, with the advantage of no significant metal ion elevation in the serum. CONCLUSION: These findings warrant the continued clinical study of compliant bearing options.

Problematic issues and conclusive remarks.

Since 2002, there has been a paradigm shift in the prevention and treatment of osteoporotic fractures. The focus now is on preventing fragility fractures and their associated complications rather than on treating low bone mineral density. Evidence shows that many patients with fractures do not undergo appropriate assessment or treatment. It is important to have an integrated approach in the overall patient management in order to address this care gap for high-risk patients.

Hip resurfacing arthroplasty: a series of 140 consecutive hips with a minimum five year follow-up. A clinical, radiological and histological analysis.

We reviewed the clinical and radiological outcome at a minimum of five years of 140 consecutive metal-on-metal hip resurfacing (HR) arthroplasties in 132 patients. The mean follow-up was 73 months (62 to 105). Revision of either component was defined as failure. The average Harris hip score (HHS) was 58.6 (25 to 88) preoperatively and 94.4 (60 to 100) at the latest follow-up (p<0.0005). Average University of California Los Angeles (UCLA) activity score was 3.1 (1 to 9) pre-operatively and 6.7 (2 to 10) post-operatively (p<0.0005). The survival after 6 years was 97.8% overall and 98.5% (excluding a post traumatic femoral neck fracture). These good medium-term results suggest that HR is an effective procedure in young and active patients.

Formulations of zero-order, pH-dependent, sustained release matrix systems by ionotropic gelation of alginate-containing mixtures.

BACKGROUND: Matrix type, monolithic, dosage forms suitable for controlled release that exhibit pH-dependent behavior are considerably less common than similarly behaving multiparticulated, enterically coated dosage forms, although simpler and less expensive to make. AIM: Evaluate the properties of alginates and alginate-containing systems to produce pH-sensitive, monolithic, controlled release dosage forms that perform acceptably and determine their limits of application in regard with stability, pH and Ca(++) sensitivity, and appropriated rate of release. METHOD: Mixtures of the ionic gum sodium alginate (Na Alg.) with other gel-forming gums such as propylene glycol alginate (PGA), xanthan, or hydroxypropyl methylcellulose have been evaluated for applicability in the manufacture of controlled release dosage forms with three drugs of different solubility and ionic character. Mixture have been compressed into tablets and tested under a variety of pHs to simulate transit through the GI tract, in the presence of Ca(++), and for stability. RESULTS: These mixtures have been able to sustain drug release for up to 12 hours with acceptable performance going from acidic to alkaline pHs to simulate travel through the GI tract and in the presence of Ca(++). Release rate has been adjusted by selecting a suitable Na Alg./other gum combination at an appropriated ratio. CONCLUSIONS: Mixtures of Na Alg. with a number of other gums have been demonstrated suitable to manufacture pH-sensitive, matrix-type solid dosage forms with release-controlling properties for up to 12 hours.

Bone mineral density of the proximal femur recovers after metal-on-metal hip resurfacing.

Bone resorption of the proximal femur is a frequent complication of total hip replacement. As hip resurfacing (HR) may load the bone more physiologically, we measured proximal femur bone mineral density (BMD) in 21 patients with HR. DEXA analysis was performed in the 7 Gruen zones and in the femoral neck pre-operatively and at 3, 9, and 24-months post-operatively. In Gruen zone-2 the BMD ratio decreased to 90±18.8% (p=0.0009) at 3-months and completely restored at 24-months to 100±17.7% (p=0.01). In Gruen zone-7 the BMD ratio decreased to 93±15.3% (p=0.05) by 3 months and surpassed the baseline to 105±14.8% (p=0.01) at 24-months. A positive correlation was observed between valgus positioning of the femoral component and BMD in Gruen zone-2 and 7 respectively. HR preserves the bone-stock of the proximal femur. When the femoral component is implanted in a valgus position BMD is further enhanced, thus potentially reducing the risk of femoral neck fractures.

Can we improve fixation and outcomes? Use of bone substitutes.

Hip fractures secondary to osteoporosis are common in the elderly. Stabilizing these fractures until union is achieved is a challenge due to poor bone stock and insufficient purchase of the implant to the bone. The reported high rate of complications has prompted extensive research in the development of fixation techniques. Furthermore, manipulation of both the local fracture environment in terms of application of growth factors, scaffolds, and mesenchymal cells and the systemic administration of agents promoting bone formation and bone strength has been considered as a treatment option with promising results. There are only a few evidence-based studies reporting on fixation augmentation techniques. This article reports on the efficacy of bone graft substitutes for the fixation of hip fractures, in particular calcium phosphates, which have been used as granules, cements, and implant coatings.

Evaluating agreement: conducting a reliability study.

Instruments that are useful in clinical or research practice will, when the object of measurement is stable, yield similar results when applied at different times, in different situations, or by different users. Studies that measure the relation of differences between patients or subjects and measurement error (reliability studies) are becoming increasingly common in the orthopaedic literature. In this paper, we identify common aspects of reliability studies and suggest features that improve the reader's confidence in the results. One concept serves as the foundation for all further consideration: in order for a reliability study to be relevant, the patients, raters, and test administration in the study must be similar to the clinical or research context in which the instrument will be used. We introduce the statistical measures that readers will most commonly encounter in reliability studies, and we suggest an approach to sample-size estimation. Readers interested in critically appraising reliability studies or in developing their own reliability studies may find this review helpful.

Fracture healing and drug therapies in osteoporosis.

Fracture repair has not been fully optimised and there is opportunity to increase the healing rate and reduce the number of complications using pharmacological means. While most anti-osteoporosis drugs have been widely tested for their ability to decrease the risk of osteoporotic fractures, fragility fractures still occur in patients under medical intervention. The primary purpose of this systematic review is to understand these underlying mechanisms between bone and drug therapies in osteoporosis and the overall promotion of fracture healing and callus formation. Databases such as MEDLINE, Google Scholar, EMBASE and CINAHL were searched and nine articles met all inclusion criteria. We report that there is still large controversy and a need for clinical trials to address the deficiencies found in animal models. There is no clear evidence yet as to whether complications during the course of healing are attributable to implant anchorage problems in osteoporotic bone or to possibly delayed healing in the aged.

A biomechanical and histological analysis of standard versus hydroxyapatite-coated pins for external fixation.

This sheep study was designed to make a comparative evaluation of two external fixation pin types each with and without hydroxyapatite (HA) coating. The two pins had different taper, pitch, and self drilling capabilities. Twenty Orthofix standard, self-tapping pins (group A), 20 Orthofix HA-coated, self-tapping pins (group B), 20 X-caliber, self-drilling, self-tapping pins (group C), and 20 X-caliber HA-coated, self-drilling, self-tapping pins (group D) were selected. Four pins were implanted in the right femurs of 20 adult sheep that were euthanized at 6 weeks. Mean pin insertion torque was 2745 +/- 822 Nmm in group A, 2726 +/- 784 Nmm in group B, 2818 +/- 552 Nmm in group C, and 2657 +/- 732 Nmm in group D (ns). Mean pin extraction torque was 1567 +/- 541 Nmm in group A, 2524 +/- 838 Nmm in group B, 1650 +/- 650 Nmm in group C, and 2517 +/- 726 Nmm in group D. HA-coated pins (group B and D) had a significantly greater mean pin extraction torque compared to similar uncoated pins (group A and C) (p < 0.0005). Histological analysis showed good osteointegration of the two coated pin types. This study shows that HA-coating is more important for optimal pin fixation than the particular combination of design parameters used in each pin type.

Fixation of HA-coated unicortical locking screws in a sheep gap model: a comparative biomechanical study.

OBJECTIVES: To evaluate whether fixing a locking compression plate (LCP) with hydroxyapatite (HA)-coated screws provides improved biomechanical fixation and healing compared with standard screws under loaded conditions. METHODS: Ten sheep were randomly divided into 2 groups. A resection osteotomy of 8 mm was performed in the sheep's right tibiae. Five tibiae were fixed with a 9-hole LCP and 8 standard unicortical locking screws (Group Non-HA), and 5 tibiae were fixed with a 9-hole LCP and 8 HA-coated unicortical locking screws (Group HA). All screws were implanted at the same insertion torque of 4000 Nmm. Three months after surgery, all the sheep were euthanized. Bone segments after screw removal were randomly chosen from each group for histologic analysis (Group Non-HA=5, Group HA=5). RESULTS: Mean screw extraction torque was 438+/-288 Nmm in Group Non-HA (n=40) and 2317+/-657 Nmm in Group HA (n=40) (P<0.0005). The tibial torque resistance of the resected tibiae was 24+/-8 Nm in Group Non-HA (n=5) and 31+/-3 in Group HA (n=5) (P=0.045). In Group Non-HA, histology showed bone resorption and fibrous tissue encapsulation in all the samples, but this was not found in any of the Group HA samples. CONCLUSIONS: This study shows that an LCP with HA-coated screws provides improved biomechanical fixation than an LCP with similar standard screws as shown by a 5-fold greater screw extraction torque (P<0.0005). Furthermore, the higher tibial torque resistance is potentially beneficial for improved gap healing, as shown by higher tibial torque resistance.

Does ion release differ between hip resurfacing and metal-on-metal THA?

UNLABELLED: Modern metal-on-metal hip resurfacing was introduced as a bone-preserving method of joint reconstruction for young and active patients; however, the large diameter of the bearing surfaces is of concern for potential increased metal ion release. We hypothesized there were no differences in serum concentrations of chromium, cobalt, and molybdenum between patients who had metal-on-metal hip resurfacing (Group A; average head diameter, 48 mm; median followup, 24 months) and patients who had 28-mm metal-on-metal THA (Group B; median followup, 25 months). Serum concentrations also were compared with concentrations in healthy subjects. We identified no differences in ion levels between Groups A and B. A distinction was made according to gender. Women showed a higher chromium release in Group A whereas men had a higher cobalt release in Group B. Values obtained from Group A were higher than those of the control subjects. Our data suggest metal-on-metal bearings for THA should not be rejected because of concern regarding potential increased metal ion release; however, patients with elevated ion levels, even without loosening or toxicity, could be at higher risk and should be followed up periodically. LEVEL OF EVIDENCE: Level III, therapeutic study. See the Guidelines for Authors for a complete description of levels of evidence.

Alendronate improves screw fixation in osteoporotic bone.

BACKGROUND: Animal studies have demonstrated the efficacy of the use of bisphosphonates to enhance screw fixation in bone. In this prospective, randomized study of pertrochanteric fractures treated with external fixation, we tested whether systemic administration of bisphosphonates would improve the fixation of hydroxyapatite-coated screws implanted in osteoporotic bone. METHODS: Sixteen consecutive patients with a pertrochanteric fracture were selected. Inclusion criteria were female gender, an age of at least sixty-five years, and a bone mineral density T-score of less than -2.5 standard deviations. Exclusion criteria included bisphosphonate treatment during the two-year period prior to the fracture. Fractures were fixed with a pertrochanteric fixator and four hydroxyapatite-coated pins. Two pins were implanted in the femoral head (pin positions 1 and 2), and two were placed in the femoral diaphysis (pin positions 3 and 4). The patients were randomized either to therapy with alendronate for a three-month postoperative period (Group A) or to no therapy (Group B). The Group-A patients received an oral dose of 70 mg of alendronate per week. The fixators were removed after three months. RESULTS: All of the fractures healed, and no loss of reduction, nonunion, or delayed union was observed. The combined mean extraction torque (and standard deviation) of the pins implanted at positions 1 and 2 (cancellous bone) was 2558 +/- 1103 N/mm in Group A and 1171 +/- 480 N/mm in Group B (p < 0.0005). The combined mean extraction torque of the pins implanted at positions 3 and 4 (cortical bone) was 4327 +/- 1720 N/mm in Group A and 4075 +/- 1022 N/mm in Group B. CONCLUSIONS: These data show that weekly systemic administration of alendronate improves pin fixation in cancellous bone in elderly female patients with osteoporosis. We observed a twofold increase in extraction torque with the pins implanted in cancellous bone. These results support the use of alendronate in the treatment of osteoporotic pertrochanteric fractures to improve screw fixation in the femoral head.

Resurrection of hip resurfacing: what is the evidence?

Total hip resurfacing has long been conceptually attractive to both surgeons and patients. However, historically it has been plagued by limited durability and marked acetabular bone loss. The recent development of wear-resistant bearings, such as metal-on-metal, has led to renewed interest in hip resurfacing in the orthopedic community. Several resurfacing implants have been designed and positive results, particularly in young patients, have been reported. Although comparative studies of hip resurfacing and standard total hip replacement are still lacking, we believe that there is now evidence to demonstrate that this surgical concept deserves consideration, particularly when treating young patients with hip diseases.

Hydroxyapatite-coated external fixation pins.

The aim of this review is to report on studies of hydroxyapatite-coated external fixation pins as a solution to enhance pin fixation. In a highly loaded animal study, three tapered pin types were compared: Type A uncoated, Type B coated with hydroxyapatite and Type C coated with titanium. There was a 13-fold increase in the extraction torque of Type B pins compared with Type A, and a twofold increase compared with Type C pins. Extraction torque was significantly lower compared with the corresponding insertion torque in both Types A (p < 0.001) and C (p = 0.003). Conversely, with the hydroxyapatite-coated pins there was no difference between extraction and insertion torque. In a clinical study of 76 external fixation pins in 19 patients treated with hemicallotasis for osteoarthritis on the medial side of the knee, pin insertion and extraction torque forces were measured. The patients were randomized to be treated with either standard tapered pins or tapered pins coated with hydroxyapatite. Extraction torque of the hydroxyapatite-coated pins was higher than the extraction torque of the standard pins in both cancellous and cortical bone (p < 0.005). In a prospective, randomized clinical study of osteoporotic wrist fractures, extraction torque of the coated pins was higher than with standard pins (p < 0.0001). These studies demonstrate that with the use of hydroxyapatite-coated pins, no deterioration of pin fixation occurs, and that there is no significant pin loosening and infection, regardless of bone type and loading conditions.

Dynamic hip screw compared with external fixation for treatment of osteoporotic pertrochanteric fractures. A prospective, randomized study.

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 degrees 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 degrees +/- 8 degrees in Group A and 2 degrees 1 degrees 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.