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Background and purpose - Limb lengthening with an intramedullary motorized nail is a relatively new method. We investigated if lengthening nails are reliable constructs for limb lengthening and deformity correction in the femur and the tibia. Patients and methods - 50 lengthenings (34 Precice and 16 Fitbone devices) in 47 patients (mean age 23 years [11-61]) with ≥12 months follow-up are included in this study. 30 lengthenings were done due to congenital and 20 because of posttraumatic deformity (21 antegrade femora, 23 retrograde femora, 6 tibiae). Initial deformities included a mean shortening of 42 mm (25-90). In 15 patients, simultaneous axial correction was done using the retrograde nailing technique. Results - The planned amount of lengthening was achieved in all but 2 patients. 5 patients who underwent simultaneous axial correction showed minor residual deformity; unintentionally induced minor deformities were found in the frontal and sagittal plane. The consolidation index was 1.2 months/cm (0.6-2.5) in the femur and 2.5 months/cm (1.6-4.0) in the tibia. 2 femoral fractures occurred in retrograde femoral lengthenings after consolidation due to substantial trauma. There were 8 complications, all of which were correctable by surgery, with no permanent sequelae. Interpretation - Controlled acute axial correction of angular deformities and limb lengthening can be achieved by a motorized intramedullary nail. A thorough preoperative planning and intraoperative control of alignment are required to avoid residual and unintentionally induced deformity. In the femur relatively fast consolidation could be observed, whereas healing was slower in the tibia.

Background and purpose — Hexapod ring fixators such as the Taylor Spatial Frame (TSF) have shown good outcomes. However, there have only been a few studies comparing the use of TSF with various etiologies of the deformity. We compared the use of TSF in congenital and acquired deformities in children. Patients and methods — We reviewed 213 lower extremity reconstructive procedures with the TSF in 192 patients who were operated between October 2000 and October 2015. 128 procedures (67 proximal tibiae, 51 distal femora, and 10 distal tibiae) in 117 children (median age 14 (4–18) years; 59 girls) fulfilled the inclusion criteria. 89 procedures were done in children with congenital deformities (group C) and 39 were done in children with acquired deformities (group A). Outcome parameters were lengthening and alignment achieved, lengthening index, complications, and analysis of residual deformity in a subgroup of patients. Results — Mean lengthening achieved was 3.9 (1.0–7.0) cm in group C and 3.7 (1.0–8.0) cm in group A (p = 0.5). Deformity parameters were corrected to satisfaction in all but 3 patients, who needed further surgery for complete deformity correction. However, minor residual deformity was common in one-third of the patients. The mean lengthening index was 2.2 (0.8–10) months/cm in group C and 2.0 (0.8–6) months/cm in group A (p = 0.7). Isolated analysis of all tibial and femoral lengthenings showed similar lengthening indices between groups. Complication rates and the need for secondary surgery were much greater in the group with congenital deformities. Interpretation — The TSF is an excellent tool for the correction of complex deformities in children. There were similar lengthening indices in the 2 groups. However, congenital deformities showed a high rate of complications, and should therefore be addressed with care.

The majority of patients with osteogenesis imperfecta (OI) have mutations in the COL1A1 or COL1A2 gene, which has consequences for the composition of the bone matrix and bone architecture. The mutations result in overmodified collagen molecules, thinner collagen fibres and hypermineralization of bone tissue at a bone matrix level. Trabecular bone in OI is characterized by a lower trabecular number and connectivity as well as a lower trabecular thickness and volumetric bone mass. Cortical bone shows a decreased cortical thickness with less mechanical anisotropy and an increased pore percentage as a result of increased osteocyte lacunae and vascular porosity. Most OI patients have mutations at different locations in the COL1 gene. Disease severity in OI is probably partly determined by the nature of the primary collagen defect and its location with respect to the C-terminus of the collagen protein. The overall bone biomechanics result in a relatively weak and brittle structure. Since this is a result of all of the above-mentioned factors as well as their interactions, there is considerable variation between patients, and accurate prediction on bone strength in the individual patient with OI is difficult. Current treatment of OI focuses on adequate vitamin-D levels and interventions in the bone turnover cycle with bisphosphonates. Bisphosphonates increase bone mineral density, but the evidence on improvement of clinical status remains limited. Effects of newer drugs such as antibodies against RANKL and sclerostin are currently under investigation. This paper was written under the guidance of the Study Group Genetics and Metabolic Diseases of the European Paediatric Orthopaedic Society. Cite this article: Nijhuis WH, Eastwood DM, Allgrove J, Hvid I, Weinans HH, Bank RA, Sakkers RJ. Current concepts in osteogenesis imperfecta: bone structure, biomechanics and medical management.

Distraction osteogenesis biologically resembles fracture healing with distinctive characteristics notably in the distraction phase of osteogenesis. In the latency phase of bone lengthening, like in the inflammatory phase of fracture repair, interleukines are released and act with growth factors released from platelets in the local haematoma, leading to attraction, proliferation and differentiation of mesenchymal stem cells into osteoblasts and other differentiated mesenchymal cells. These in turn produce matrix, collagen fibers and growth factors. A callus containing cells, collagen fibers, osteoid and cartilage matrix is formed. Provided stable fixation, distraction will trigger intramembranous bone formation. As distraction proceeds, the distraction gap develops five distinctive zones with unmineralized bone in the middle, remodelling bone peripherally, and mineralizing bone in between. During consolidation, the high concentration of anabolic growth factors in the regenerate diminishes with time as remodelling takes over to form mature cortical and cancellous bone. Systemic disease, congenital bone deficiencies, medications and substance abuse can influence the quality and quantity of regenerate bone, usually in a negative way. The regenerate bone can be manipulated when needed by using injection of mesenchymal stem cells and platelets, growth factors (BMP-2 and -7), and systemic medications (bisphosphonates and parathyroid hormone). Growth factors and systemic anabolic and antiresorptive drugs are prescribed on special indications, while distraction osteogenesis is not an authorized indication. To some extent, however, these compounds can be used off-label. Use in children presents special problems since growth factors and specific anabolic medications may involve a risk of inducing cancer.

Objective: Bioabsorbable barrier membranes placed over alveolar ridge bone defects are routinely used in dental surgery to promote bone formation. Combining these osteoconductive membranes with osteoinductive Bone Morphogenetic Proteins could prove useful in long bone fracture treatment. The hypothesis was tested in a clinically relevant model of compromised healing. Methods: Four groups of 8 rabbits underwent unilateral mid-tibial osteotomy, excision of periosteum and endosteum, and plate fixation. One group had rhBMP-2 deposited between the bone ends and Membrane wrapped around the osteotomy, the second group had Membrane wrapped around the osteotomy, the third group had rhBMP-2 placed between the bone ends, and the fourth group received no additional treatment. Results: After 7 weeks, callus size and blood flow were significantly higher in the Membrane+rhBMP-2 group than in the rhBMP-2 treated group, but torsion to failure test showed no significant difference. Membrane treatment and no treatment led to non-union. Conclusion: Absorbable barrier membrane combined with rhBMP-2 enhances bone formation, but has no advantage to rhBMP-2 alone. Membrane alone wrapped around the osteotomy was unable to prevent non-union formation.

We assessed whether increase of subchondral bone density enhances cartilage stress during impact loading, leading to progressive cartilage degeneration and accelerated osteoarthrosis (OA) progression. Sixty-six male guinea pigs were randomly divided into six groups. During a 9-week treatment period, four groups received twice-weekly subcutaneous injections of alendronate (ALN) in two doses: two groups received 10 microg/kg and two groups received 50 microg/kg. The two control groups received vehicle. After 9 weeks, one 10 microg/kg ALN group, one 50 microg/kg ALN group, and one control group were killed. The remaining three groups (17-week groups) were left for an additional 8 weeks, receiving the same treatment regimen before death. The left proximal tibiae were scanned by micro-computed tomography to quantify the microarchitecture of subchondral bone, followed by mechanical testing and determination of collagen and mineral. The control groups had typical OA-related cartilage degeneration at 9 and 17 weeks, whereas the 50 microg/kg ALN group had even worse degeneration in the medial condyle. It is unclear whether there is a direct or a secondary effect of ALN on the cartilage. The 9-week ALN group had significantly greater subchondral plate thickness. The 9- and 17-week groups had similar changes of cancellous bone microarchitecture, with greater volume fraction and connectivity and an extremely plate-like structure. The 9-week ALN group had greater bone mineral concentration, and the 17-week ALN group had reduced collagen concentration and greater mineral concentration. Treatment with ALN did not significantly change the mechanical properties of the cancellous bone.

Introduction: Therapeutic angiogenesis, a novel concept in tissue engineering, is neo-formation of blood vessels in a tissue upon delivery of an angiogenic growth factor to the tissue. We hypothesised that therapeutic angiogenesis could enhance bone formation and challenged the hypothesis in an experimental model of distraction osteogenesis. Methods: Rabbits, divided into three equal groups of 12, had their right tibia lengthened by distraction osteogenesis. A mini-osmotic pump delivered to the osteotomy gap either recombinant human vascular endothelial growth factor (VEGF), VEGF-inhibitor, or vehicle alone during the latency and distraction phase. After consolidation, we assessed bone blood flow by radioactive microsphere entrapment, measured torsional stiffness and bone mineral content, and did histomorphometry. Results: VEGF and VEGF-inhibitor treatment failed to influence bone blood flow, torsional stiffness, bone mineral content and histomorphometric indices of the bone regenerate. However, VEGF treatment increased the blood flow in bone of the distracted limb and VEGF-inhibitor treatment decreased bone blood flow. Conclusion: The regenerate was unresponsive to VEGF and VEGF-inhibitor treatment in contrast to the neighbouring bone, which implies different biological properties of the vasculature in native and regenerating bone. VEGF is not recommended for enhancement of bone formation in this setting.

We have reviewed at an average period of ten years the results of 71 consecutive primary arthroplasties with the Insall-Burstein total condylar knee prosthesis in patients with rheumatoid arthritis. Their mean age at surgery was 52 years (24 to 72). At follow-up the overall results (Hospital for Special Surgery knee rating score) were excellent or good in 77%, fair in 11% and poor in 11%. There was residual pain in only 5% of patients with prostheses in situ; 58% could walk more than 500 m, and the median range of motion was 108 degrees. Eight knees had been revised. Five underwent arthrodesis because of deep infection and three needed revision arthroplasty for mechanical loosening. The crude survival rate of the arthroplasties was 89%. The presence of radiolucency around the tibial component correlated significantly with the severity of residual pain.

Udgivelsesdato: 2009-Dec BACKGROUND AND PURPOSE: Parathyroid hormone (PTH) has attracted considerable interest as a bone anabolic agent. Recently, it has been suggested that PTH can also enhance bone repair after fracture and distraction osteogenesis. We analyzed bone density and strength of the newly regenerated mineralized tissue after intermittent treatment with PTH in rabbits, which undergo Haversian bone remodeling similar to that in humans. METHODS: 72 New Zealand White rabbits underwent tibial mid-diaphyseal osteotomy and the callus was distracted 1 mm/day for 10 days. The rabbits were divided into 3 groups, which received injections of PTH 25 microg/kg/day for 30 days, saline for 10 days and PTH 25 microg/kg/day for 20 days, or saline for 30 days. At the end of the study, the rabbits were killed and the bone density was evaluated with DEXA. The mechanical bone strength was determined by use of a 3-point bending test. RESULTS: In the 2 PTH-treated groups the regenerate callus ultimate load was 33% and 30% higher, absorbed energy was 100% and 65% higher, BMC was 61% and 60% higher, and callus tissue volume was 179% and 197% higher than for the control group. INTERPRETATION: We found that treatment with PTH during distraction osteogenesis resulted in substantially higher mineralized tissue volume, mineral content, and bending strength. This suggests that treatment with PTH may benefit new bone formation during distraction osteogenesis and could form a basis for clinical application of this therapy in humans.

This issue of Acta presents two articles dealing with (1) early diagnosis of neonatal hip instability (NHI) (Finne et al. 2008), and (2) the associated risk of total hip replacement (THR) in young ...

The overall purpose of the study is to determine the effects of parathyroid hormone (PTH) (1-34) on bone formation in regenerated and surrounding bone of distracted callus during limb lengthening in rabbits. Additionally the aim of the pilot study is to titrate the optimal dose of PTH for distraction osteogenesis treatment in rabbits' tibial lengthening model.A total of 18 rabbits underwent right tibia lengthening by callus distraction. Lengthening was started 5 days postoperatively 1 mm/day for a 10-day period and consolidation of 20 days followed. Rabbits were divided into three groups: group I received PTH (1-34) treatment at a dose of 5 microg/kg/day, group II received treatment with PTH (1-34) at a dose of 25 microg/kg/day; group III rabbits were treated with saline. After euthanasia, tibiae of both legs were dissected free, kept frozen and underwent x-ray analysis, dual x-ray absorptiometry-scanning, microcomputed tomography scanning and three-dimensional evaluation and mechanical test followed.Over all, during distraction osteogenesis in a new regenerated bone, PTH (1-34) treatment with two different doses of 5 microg/kg/day and 25 microg/kg/day increased callus cross-sectional area, callus bone mineral density and bone mineral content, bone volume density; dramatically increased trabecular number with slight increase in trabecular thickness, whereas decreased trabecular separation, bone surface density and decreased degree of anisotropy when compared to control group animals.PTH (1-34) treatment improved mineralization, structural indices of regenerated distracted rabbits' tibiae, whereas treatment at a dose of 25 microg/kg/day PTH (1-34) was significantly more effective than 5 microg/kg/day PTH(1-34) dose treatment when compared to control group. Bigger dose has been chosen for the main study.

Distraction osteogenesis can be used for the treatment of osteomyelitis and nonunion, conditions thought to benefit from increased blood flow in the bone tissue of the distracted limb. We have questioned whether such an increase occurs, and investigated the spatial distribution of bone blood flow after distraction osteogenesis.The tibiae of 8 rabbits were lengthened 10 mm by a standard midtibial distraction osteogenesis procedure. 2 weeks into the consolidation phase, the bone and soft tissue blood flow of the distracted and the contralateral extremity were measured using radioactive microspheres.The absolute bone blood flow of the distracted tibia was 4% lower than that of the non-distracted side, representing a 41% decrease in the proximal metaphysis, a smaller decrease in the proximal epiphysis, distal metaphysis and distal epiphysis, and an increase in the diaphysis.Mid-tibial distraction osteogenesis redistributed the bone blood flow of the distracted tibia, but absolute tibial blood flow did not increase. Our results do not confirm previous research in this field.

Parathyroid hormone naturally secreted by the parathyroid glands is a potent anabolic agent for bone. Parathyroid hormone is primarily thought of as a catabolic protein involved in the physiologic release of calcium from bone. Whereas during recent years, a number of animal studies and clinical trials have demonstrated that intermittent parathyroid hormone administration induces anabolic effects on both cancellous and cortical bone, enhances bone mass and increases mechanical strength of the bones. Most of the studies, both animal and human, have addressed the treatment of osteoporosis and parathyroid hormone represents an important new advance in the therapy of osteoporosis. Few studies have investigated the effect of intermittent parathyroid hormone treatment in the field of orthopedics on fracture healing and fixation of orthopedic implants. The results of those studies indicated an enhancement of fracture healing, faster bone repair and better fixation of the implant. Recently there were few animal studies started to investigate the effects of parathyroid hormone treatment on bone formation in regenerated and surrounding bone of distracted callus during limb lengthening. Distraction osteogenesis is a technique for bone lengthening that is widely used clinically and experimentally. Newly forming bone during distraction osteogenesis is expected to be an appropriate pattern for parathyroid hormone anabolic effect. Preclinical studies as well as clinical trials suggest that parathyroid hormone might be useful as a stimulator of bone formation whereas a lot of questions regarding parathyroid hormone therapy remain unanswered and require further experimental studies and investigations.

Hyaluronan (HA) has received increasing interest as a potential agent in therapeutic intervention in osteoarthrosis (OA). HA has been shown to reduce arthritic lesions in experimental animal models of articular cartilage injury. This study was to investigate the effects of high molecular weight HA intra-articular injection on subchondral bone tissues. Fifty-six male guinea pigs were randomly divided into 5 groups. During the initial 2.5-month period, three groups received intra-articular injection of HA 0.4 mg/kg/week for 5 weeks in both knee joints. Two control groups received vehicle. After 2.5 months, one HA group and one control group were sacrificed. The remaining 3 groups (5.5-month groups) were left for an additional 3 months before sacrifice during which time one HA group received additional 5 weeks injections, one HA group received no more injections, and the control group received vehicle. The left tibiae were harvested and micro-CT scanned to quantify three-dimensional microarchitecture of subchondral bone plate, cancellous bone and cortical bone, followed by mechanical testing and collagen and mineral determinations. All HA-treated groups had almost normal cartilage, whereas the control groups had typical OA-related cartilage degradation. In the 2.5-month group, HA resulted in significantly decreased subchondral plate volume fraction and thickness and HA-treated cancellous bone had significantly lower bone volume fraction, and typical rod-like structure. After 5.5 months, these changes were more pronounced, with an additional marked decrease in connectivity and bone surface density. HA-treated cortical bone had significantly greater volume fraction at both observation times. HA groups had greater bone mineral concentration and reduced collagen to mineral ratio with similar mechanical properties of cancellous bone but less stiff cortical bone. The effects of HA on cartilage and subchondral bone were maintained when treatment was discontinued. In summary, HA effectively protects against cartilage degeneration, decreases subchondral bone density and thickness, changes trabecular structure toward rod-like, so that subchondral bone becomes more compliant and thereby reduces cartilage stress during impact loading. HA preserved cancellous bone mechanical properties by increasing bone mineralization. Early HA administration is effective for intervention of OA initiation and progression, and short-term early HA treatment is sufficient to maintain treatment effects.

A thorough understanding of the microstructure of cancellous bone is crucial for diagnosis, prophylaxis, and treatment of age-related skeletal diseases. Until now, little has been known about age-related variations in the microstructure of peripheral cancellous bone. This study quantified age-related changes in the three-dimensional (3D) microstructure of human tibial cancellous bone. One hundred and sixty cylindrical cancellous bone specimens were produced from 40 normal proximal tibiae from 40 donors, aged 16–85 years. These specimens were micro-computed tomography (micro-CT) scanned, and microstructural properties were determined. The specimens were then tested in compression to obtain Young's modulus. The degree of anisotropy, mean marrow space volume, and bone surface-to-volume ratio increased significantly with age. Bone volume fraction, mean trabecular volume, and bone surface density decreased significantly with age. Connectivity did not have a general relationship with age. Bone volume fraction together with anisotropy best predicted Young's modulus. Age-related changes in the microstructural properties had the same trends for both medial and lateral condyles of the tibia. The observed increase of anisotropy and constant connectivity suggest a bone remodeling mechanism that may reorient trabecular volume orientation in aging tibial cancellous bone. The aging trabeculae align more strongly to the primary direction – parallel to the tibial longitudinal loading axis.

Subchondral cancellous bone specimens were removed from 10 human postmortem early-stage arthrotic proximal tibiae (mean age 73 (63-81) years) and 10 age- and gender-matched normal proximal tibiae. The early-stage arthrosis was confirmed histologically and the specimens were divided into 4 groups: medial arthrosis, lateral control, normal medial and normal lateral controls. The specimens were tested in compression to determine mechanical properties and then physical/compositional properties. Compared to the normal medial control, we found reductions in ultimate stress, Young's modulus, and failure energy, and an increase in ultimate strain of arthrotic cancellous bone. Bone volume fraction, apparent density, apparent ash density, and collagen density were higher in cancellous bone with arthrosis, but no differences were found in tissue density, mineral and collagen concentrations between arthrotic cancellous bone and the 3 controls. None of the mechanical properties of arthrotic cancellous bone could be predicted by the physical/compositional properties measured. The increase in bone tissue in early-stage arthrotic cancellous bone did not make up for the loss of mechanical properties, which suggests a deterioration in the quality of arthrotic cancellous bone.

Unbiased stereological methods were used in conjunction with microcomputed tomographic (micro-CT) scans of human and animal bone to investigate errors created when the parallel plate model was used to calculate morphometric parameters. Bone samples were obtained from the human proximal tibia, canine distal femur, rat tail, and pig spine and scanned in a micro-CT scanner. Trabecular thickness, trabecular spacing, and trabecular number were calculated using the parallel plate model. Direct thickness, and spacing and connectivity density were calculated using unbiased three-dimensional methods. Both thickness and spacing calculated using the plate model were well correlated to the direct three-dimensional measures (r(2) = 0. 77-0.92). The correlation between trabecular number and connectivity density varied greatly (r(2) = 0.41-0.94). Whereas trabecular thickness was consistently underestimated using the plate model, trabecular spacing was underestimated at low volume fractions and overestimated at high volume fractions. Use of the plate model resulted in a volume-dependent bias in measures of thickness and spacing (p < 0.001). This was a result of the fact that samples of low volume fraction were much more "rod-like" than those of the higher volume fraction. Our findings indicate that the plate model provides biased results, especially when populations with different volume fractions are compared. Therefore, we recommend direct thickness measures when three-dimensional data sets are available.

Cylindrical human tibial cartilage-bone unit specimens were removed from 9 early-stage medial osteoarthrotic (OA) tibiae (mean age 74 years) and 10 normal age-matched tibiae (mean age 73 years). These specimens were divided into 4 groups: OA, lateral comparison, medial age-matched, and lateral age-matched and were tested to 0.5% bone strain with a novel technique to obtain the stiffnesses of both cartilage and bone simultaneously. We found a pronounced reduction in the stiffnesses of OA cartilage and subchondral bone when compared with the medial age-matched group. OA cartilage was significantly thinner than that of the lateral comparison and the medial age-matched control groups. However, this reduction in thickness was not correlated with the reduction in stiffness for OA cartilage. The stiffnesses did not correlate between OA cartilage and bone, whereas the stiffness relationships between cartilage and bone remained significant in the three control groups. Our findings suggest that both cartilage and bone in early-stage OA are mechanically inferior to normal, and that OA cartilage and bone have lost their unit function to mechanical loading.

We investigated changes in periosteal insulin-like growth factor I (IGF-I) during tibial lengthening. In 37 rabbits, an osteotomy of the right middle tibia was made and fixed by a unilateral external fixator. The rabbits were randomized into 6 groups: the tibiae were distracted at 0.5 mm/day up to 4 weeks and the animals killed after 2 weeks, 4 weeks or 6 weeks, for each period there was a control group with no distraction. Periosteal IGF-I was measured by radioimmunoassay and bone formation was quantified by CT scanning. During bone lengthening, CT showed moderate bone formation, while IGF-I was increased. When lengthening was stopped, IGF-I returned to a basal level, and CT scanning showed considerable bone formation. Our study suggests that IGF-I plays a role in an early stage of bone formation.

We investigated changes in the anterior tibial muscle during lengthening of the lower leg in rabbits. In 37 rabbits, an osteotomy of the right middle tibia was performed and was fixed by a unilateral external fixator. The rabbits were randomized into 6 groups. In groups 1, 2, and 3 the tibiae were distracted 0.5 mm/day. In groups 1 and 2, the rabbits were killed after 14 and 28 days of distraction, respectively, and in group 3 after 28 days of distraction, followed by 14 days of rest. Groups 1a, 2a, and 3a served as controls. They were treated similarly as groups 1, 2, and 3, but no distraction was performed. Proliferating cell nuclei were labeled with 5-bromo-2-deoxyuridine and were identified by immunohistochemical staining. The weight of the muscle was measured. During bone lengthening the muscle showed signs of growth, as indicated by increasing weight and number of proliferating cell nuclei. This was observed only during lengthening and it ceased when the lengthening was stopped.

The results of 138 consecutive primary Insall-Burstein arthroplasties with an average observation period of 10 (9-11) years were assessed. Mean age at surgery was 71 (30-81) years. The patients were evaluated clinically, using the Hospital for Special Surgery knee rating scale, and radiographically, according to the radiolucency score of the Knee Society. At latest follow-up, the overall evaluation of the patients who completed the study was excellent or good in 86 percent, fair in 8 percent and poor in 6 percent. Residual functional pain was recorded in 12 percent of cases with prostheses in situ. An ability to walk more than 500 m was found in 62 percent. The median range of motion was 104 degrees. Arthrodesis was performed on 2 knees due to deep infection. There were 14 cases with substantial radiolucency around the prosthesis, but none of these patients had severe functional pain. The crude prosthetic survival rate was 98 percent. A correlation was found between the radiolucency score and both the total score and the intensity of the residual functional pain.

We assessed whether increase of subchondral bone density enhances cartilage stress during impact loading, leading to progressive cartilage degeneration and accelerated osteoarthrosis (OA) progression. Sixty-six male guinea pigs were randomly divided into six groups. During a 9-week treatment period, four groups received twice-weekly subcutaneous injections of alendronate (ALN) in two doses: two groups received 10 μg/kg and two groups received 50 μg/kg. The two control groups received vehicle. After 9 weeks, one 10 μg/kg ALN group, one 50 μg/kg ALN group, and one control group were killed. The remaining three groups (17-week groups) were left for an additional 8 weeks, receiving the same treatment regimen before death. The left proximal tibiae were scanned by micro-computed tomography to quantify the microarchitecture of subchondral bone, followed by mechanical testing and determination of collagen and mineral. The control groups had typical OA-related cartilage degeneration at 9 and 17 weeks, whereas the 50 μg/kg ALN group had even worse degeneration in the medial condyle. It is unclear whether there is a direct or a secondary effect of ALN on the cartilage. The 9-week ALN group had significantly greater subchondral plate thickness. The 9- and 17-week groups had similar changes of cancellous bone microarchitecture, with greater volume fraction and connectivity and an extremely plate-like structure. The 9-week ALN group had greater bone mineral concentration, and the 17-week ALN group had reduced collagen concentration and greater mineral concentration. Treatment with ALN did not significantly change the mechanical properties of the cancellous bone.

We measured the changes of bone density by computed tomography of the proximal tibia after total knee replacement in 18 patients, 9 with arthrosis and 9 with rheumatoid arthritis. All the patients had good results after 1 and 2 years. There were no significant radiolucencies at the cement-bone interface. At the early postoperative measurements, we found abnormal mediolateral distributions of density, closely related to the preoperative tibiofemoral angle (r = -0.67). This distribution was within normal limits after 3 months in knees with preoperative valgus and after 2 years in knees with preoperative varus. The mean tibial density did not differ between patients with arthrosis and rheumatoid arthritis at the early postoperative examination, but the density in rheumatoid patients decreased by one third during the 2-year period. Although the overall change after knee replacement was loss of density, the preoperatively less loaded condyles had a slight tendency towards increasing density with time, a response that was considerable in some cases.

Prosthetic positioning and overall postoperative alignment were studied in 138 consecutive total knee replacements, using the Insall/Burstein total condylar knee system. Overall alignment was within 7 +/- 5 degrees of valgus in 63 per cent of the knees, while tibial component positioning was within 4 degrees of tilt in any direction in 53 per cent of the knees. A radiolucency index incorporating width and extent of radiolucent zones at the tibia was shown to progress from 3 months to 2 years postoperatively. The radiolucency index 2 years postoperatively was higher with postoperative varus alignment in the rheumatoid arthritis group; a tibial component tilt of more than 4 degrees in any direction increased the radiolucency index in both treatment groups.

During a ten-year period 193 patients with an appendiceal mass--and subsequently proved postinflammatory changes of the appendix--were treated conservatively. The course was uneventful in 88%. Twelve per cent underwent delayed surgical intervention caused by complications with one death. Elective appendectomy was performed after three months with a complication rate of 3.4%. In comparison with series with early operation the conservative management seems to carry a lower morbidity. The value of elective appendectomy is discussed.

Twenty-two patients treated non-operatively for chondromalacia patellae were followed up after an average of 5.7 years in order to evaluate the effect of abnormal patellofemoral biomechanics on the natural history of the symptoms. Clinical and radiological investigation revealed 15 patients with signs of malalignment, femoral trochlear dysplasia or excessive lateral pressure syndrome, 3 patients with marginal signs of malalignment and 4 patients with no demonstrable abnormalities. A statistically significant difference in the evolution of symptoms between the normal and the abnormal group is demonstrated, 14 out of 15 in the latter group having unchanged or worsened symptoms. The stage of chondromalacia change as judged arthrographically at the beginning of the observation period did not influence the clinical outcome.

Sixty-six knees were investigated to obtain paired values of patellar tendon/patella ratios and sulcus angles as an expression of patellar height and femoral trochlear development respectively. There was a highly significant statistical correlation between the two measurements, high riding patellae occurring with shallow trochleae.

In 29 patients with patellofemoral complaints paired values of Q-angle and internal hip rotation were determined. In addition the patellar height index of InsallSalvati (1971) was calculated from measurements on lateral radiographs of the knees. Both Q-angle and internal hip rotation were significantly higher in women than in men and there was a statistically significant correlation between these two measurements. There was no significant correlation between Q-angles and patellar height indexes. As external hip rotation can generally be taken as a measure of internal femoral torsion, these findings favour the hypothesis of a torsional malalignment syndrome of the patellofemoral joint.

Non-destructive measurements of compressive stiffness were carried out on 20 proximal tibial autopsy specimens. The tibial epiphyses were first loaded through a template covering all but the peripheral 2 mm of the subchondral resection surface, then through the whole resection surface, and finally, after removal of the peripheral shell. A slight increase of the stiffness coefficient resulted from peripheral contact. Stiffness increased significantly after removal of the shell, but several potential sources of systematic error in this part of the investigation raise questions as to the validity of this finding. The area-corrected stiffness showed a decrease as a result of peripheral contact; this result indicates that the peripheral rim of bone has a lower area-corrected stiffness than the central bone, a finding which is incompatible with the concept of a true cortical shell at the epiphyseal level.

The topographic variation of proximal tibial cancellous bone strength was investigated in 12 knees from routine autopsies. Samples from eight knees were tested to compressive failure in an Instron® material testing machine, and four knees were tested with the osteopenetrometer, an instrument developed for intraoperative measurement of bone strength. Ultimate stress, elastic modulus and energy absorption of the bone were calculated from the Instron-curves. Mechanical properties varied considerably from knee to knee, but the topographic patterns were remarkably constant. The medial condyle showed the highest strength, the intercondylar area the lowest. On the medial side the bone was strongest at the front, while on the lateral side the reverse was true. The two horizontal levels tested did not differ significantly. The osteopenetrometer measurements closely modelled the pattern of ultimate stress.

A case of bilateral hallux saltans in a 13-year-old girl is reported. The signs and symptoms were a tender nodule behind the medial malleolus and a “trigger toe” as well as pain radiating up the lower leg. Operation revealed thickening of the flexor retinaculum superficially to the flexor hallucis longus tendon which showed compression and proximal thickening. Resection of the retinaculum afforded a satisfactory result.

A case of clinically successful autografting of rib perichondrium to the patella in a 55-year-old woman suffering from painful traumatic chondromalacia patellae is reported. A postoperative arthrogram however did not show any significant regeneration of cartilage but arthroscopy revealed a smooth surface of cartilage on the patella. Biopsies were not performed.