Recent reports suggest that long-term alendronate therapy may result in an unusual pattern of femoral subtrochanteric fracture. We aimed to determine if the presence of a specific radiographic feature in patients on alendronate could be used to predict an impending insufficiency fracture and thereby prevent its occurrence through further investigations and prophylactic fixation in high-risk patients.

Sixty-two subtrochanteric fractures treated surgically from 2001 to 2007 were reviewed and radiographs of 25 low-energy fractures were independently evaluated. Incidence of alendronate therapy, clinical data, and other investigations like bone mineral density (BMD) scans were recorded.

Seventeen fractures (68%) were associated with alendronate therapy. Hypertrophy of the lateral cortex of the femur with splaying of the fracture ends was noted in 70.1% of patients on alendronate; initial radiographs were not available in 17.6% and 11.8% had stress fractures identified by bone scan. None of the fractures in the non-alendronate group had this pattern. The fracture configuration in the alendronate group suggested that an ellipsoid thickening in the lateral cortex had been present prior to fracture. Indeed, 6 patients on alendronate (35.3%) had pre-existing radiographs as early as 3 years prior to fracture and all had this feature. Four of them had bone scans, which confirmed a stress fracture. Hip pain was often associated with this radiographic sign but may not be specific as patients were already on follow-up for other musculoskeletal conditions. BMD scans were not predictive of an impending fracture as they were mostly in the osteopaenic range. Only 50% with proven stress fractures had prophylactic fixation, while the remainder sustained overt fractures.

Alendronate-related subtrochanteric fractures are associated with a specific pre-existing radiographic abnormality. We recommend that all patients on long-term alendronate - particularly those with hip pain or a previous subtrochanteric fracture - be routinely followed-up with plain radiographs of the pelvis. If an ellipsoid feature is noted in the subtrochanteric region, further investigations like bone scan or MRI should be sought. Patients with evidence of stress fracture should be strongly considered for prophylactic operative fixation. We believe this is a cost-effective strategy to prevent subtrochanteric insufficiency fractures in patients on alendronate.

Carbon fibre reinforced polyetheretherketone (CFR-PEEK) has been introduced recently as an alternative material to be used in joint prostheses. During injection moulding of the CFR-PEEK the carbon fibres tend to become orientated in the direction of the plastic flow. The direction of these fibres may affect the wear produced by these materials.

Reciprocation only and reciprocation plus rotation (multi-directional) pin-on-plate wear tests were performed on PAN-based CFR-PEEK against itself. The plates were manufactured with the carbon fibres mainly orientated either longitudinally (in the direction of reciprocation motion) or mainly transversally (perpendicular to the direction of motion) to determine the effect of carbon fibre orientation on the wear of these materials. For each test, four pin and plate samples were tested (two reciprocation only and two reciprocation plus rotation) for three and a half million cycles at a cycle frequency of 1 Hz under a 40 N load (which resulted in a contact stress of about 2 MPa). The lubricant used was bovine serum diluted with de-ionised water to a protein content of 17 gl-1. This was maintained at 37 °C. The wear was determined gravimetrically. Soak control specimens were used to account for any weight changes due to lubricant absorption.

The average steady-state wear for the CFR-PEEK samples that underwent reciprocation motion only was found to be 5.41 and 18.7 × 10-8 mm3N-1m-1 for the longitudinal carbon fibres and the transverse fibres respectively. For the multi-directional tests, the average steady-state wear was 5.88 and 19.9 × 10-7 mm3N-1m-1 for the longitudinal and transverse fibres respectively. It is clear from these results that for both reciprocation motion only and reciprocation plus rotation the wear was considerably lower with the fibres orientated in the longitudinal direction than the transverse direction. Also, these tests show that reciprocation only gives approximately an order of magnitude lower wear than multi-directional motion.

It can be concluded that the wear rate of CFR-PEEK is lower when the sliding motion occurs in the same direction as the carbon fibre orientation. Also, in these pin-on-plate tests, the wear produced using reciprocation motion only was an order of magnitude lower than that for the tests using multi-directional motion.

The authors wish to thank INVIBIO Ltd for funding this research.

Introduction: Treatment of hip joint disease with Total Hip Arthroplasty (THA) is in continuous evolution with new approaches, new size of components and type of bearing surfaces. Meanwhile, the analyses of proven implants continues to yeld results with a high survivor-ship and almost absent osteolysis, even with the greater wear found in the poliethylene (PE) insert of 10 to 15 year old implants. The results of these THA and the need to revise some implants not loosened but with wear of the PE, is the object of this study.

Methods: 330 non-cemented THA with the CLS expansion cup, performed by four surgeons over 15 years, are retrospectively analyzed. General anthropometric data of the studied population was obtained from medical records. Clinical elements are evaluated, among others the diagnosis, size and orientation of the components, time of partial/total weight bearing, period of crutch assisted walking, subjective patient satisfaction.

X-rays were measured for numerical assessment of the orientation of the cup, migration, radiolucent lines, osteolysis and indirect evaluation of the wear of the PE insert. Obtained data recorded over the life of the implant was computed for correlations. Other studied elements include survival rate, complication, occurrence and type of revisions.

Results: The encountered populations age was 62.7 +/− 10.9 years (Min 20, Max 86), the sex 43.1% male 56.9% female, the affected side 53.5% right 46.5% left. Charts of clinical elements, radiological measurements and correlation studies are presented. The wear of the PE insert correlates with the age of the implant and the inclination of the cup but not with radiolucent lines or osteolysis, which have a very low incidence. The complications and the survivorship analysis of the implants are presented and discussed. The encountered revision rate was 2.3% in the studied population. Without loosening, most revisions consisted on simple PE and head exchange.

Conclusions: In the authors’ opinion, the very high rate of long-term survivorship with the CLS expansion cup makes this an excellent implant for THA. Even in the 10 to 15 year old group of implants presenting greater wear of PE, there is very low presence of osteolysis and low rate of loosening, permitting to perform simple exchange of the insert and head, a simple revision procedure that will allow quick functional recovery, high patient satisfaction and a good cost/efficiency relationship.

Malfunctioning of Total Knee Replacements is often related to patella-femoral problems. As the patella groove guides the patella during flexion, the difference between anatomic- and prosthetic groove geometry may be of major influence concerning patella-femoral problems. This study focusses on the orientation or direction of the femoral patella groove, relative to the mechanical axis of the femur. Literature shows a controversy in measured groove orientation: Eckhoff et al. (1996) have measured a lateral groove, and Feinstein et al. (1996) have measured a medial groove, relative to the mechanical axis. Current femoral knee components have a lateral, or neutral directed patella groove. As most TKA surgical techniques subscribe an exorotation of the femoral component during implantation, the prosthetic in vivo situation will show a lateral groove. The objectives were to clarify the described controversy and to determine whether there is a difference in anatomic- and prosthetic groove orientation, which might cause patella-femoral problems.

The patella groove orientation of 100 human femora was measured using a 3-D measurement system. A spherical measurement probe was moved through the groove, starting at the notch and finishing at the cartilage edge, to simulate patella motion. The patella groove angle was defined as the angle between the mechanical axis and the measured groove points, in the frontal plane. A medial patella groove angle of 1.8±2.6° was measured. An implanted situation of a femoral component with neutral groove showed a lateral groove angle of 1.3°. An implanted situation of a femoral component with assymmetrical groove showed a lateral groove angle of 2.6°. The authors measured a medial oriented patella groove. This anatomical groove orientation is in contradiction with current femoral knee component design and surgical practice, because that results in a lateral oriented groove. This difference in anatomic- and prosthetic groove orientation may be a cause of patella-femoral problems.

In a prospective study of 14 patients undergoing total hip replacement we have used dual-energy X-ray absorptiometry (DEXA) to investigate remodelling of the bone around two different designs of cementless femoral prosthesis. The bone mineral density (BMD) was measured at 12-weekly intervals for a year. Eight patients (group A) had a stiff, collarless implant and six (group B) a flexible isoelastic implant.

Patients in group A showed a decrease in BMD from 14 weeks after operation. By 12 months, the mean loss in BMD was 27%, both medially and laterally to the proximal part of the implant. Those in group B showed an overall increase in BMD which reached a mean of 12.6% on the lateral side of the distal portion of the implant.

Our results support the current concepts of the effects of stem stiffness and flexibility on periprosthetic remodelling.

A lesion similar to that described by Bankart in recurrent dislocation of the shoulder was seen in seven patients with recurrent dislocation of the peroneal tendons. Detachment of the periosteum had resulted in the formation of a false pouch on the surface of the lower end of the fibula; into this pouch the peroneal tendons could easily dislocate. Reattachment of the periosteum to drill holes in the fibula prevented dislocation, and this anatomical method of repair is described. This lesion is one of the causes of recurrent dislocation of the peroneal tendons.

The joint surfaces of 60 hips obtained from the cadavers of elderly Asians were studied to determine the incidence, the grade and the distribution of both non-progressive (age-related) and progressive degenerative changes. It was observed that in the Asian population of 40 to 90 years of age, non-progressive changes were common, being seen in 66% of the acetabular specimens and 50% of the femoral heads. Only one specimen of the 60 showed unexplained progressive degenerative change. We conclude that primary osteoarthritis of the hip is rare in Asians.

Four patients with lumbosacral fracture-dislocation are presented. The common mechanism of injury was hyperflexion with compression. A rotational element may be implicated in single facet dislocation. Although lumbosacral fracture-dislocations can be managed conservatively, the best method of treatment is open reduction and bone grafting as soon after injury as possible. Only this will ensure complete correction of the deformity and prevent later deterioration.