Local bisphosphonate reduces migration and formation of radiolucent lines adjacent to cemented acetabular components.

AIMS: Post-operative migration of cemented acetabular components as measured by radiostereometric analysis (RSA) has a strong predictive power for late, aseptic loosening. Also, radiolucent lines predict late loosening. Migration has been reduced by systemic bisphosphonate treatment in randomised trials of hip and knee arthroplasty. Used as a local treatment, a higher local dose of bisphosphonate can be achieved without systemic exposure. We wished to see if this principle could be applied usefully in total hip arthroplasty (THA). PATIENTS AND METHODS: In this randomised placebo-controlled, double-blinded trial with 60 participants, we compressed gauze soaked in bisphosphonate solution (ibandronate) or saline against the acetabular bone bed immediately before cementing the acetabular component. RSA, classification of radiolucent lines, the Harris Hip Score (HHS) and the Western Ontario McMasters Universities Osteoarthritis Index (WOMAC) were carried out at three-, six-, 12-, and 24-month follow-up. RESULTS: Migration of the cemented acetabular component relative to the pelvis was reduced by movement almost half in the ibandronate group, when measured as maximum total point or as movement of the femoral head (p = 0.001 and 0.004, respectively). Radiolucent lines after one year were classified as absent, partial or complete, and correlated with treatment (rho 0.37; p = 0.004). Only three of 30 patients in the ibandronate group had complete lines, compared with 13 of 28 in the placebo group (p = 0.002). There were no significant effects on HHS or WOMAC score. CONCLUSION: Considering the power of RSA to predict loosening of cemented acetabular components, and the likelihood that radiolucent lines indicate risk of loosening, these data suggest that local treatment with a bisphosphonate can reduce the risk of late aseptic loosening. Cite this article: Bone Joint J 2017;99-B:317-24.

Internal fixation versus total hip arthroplasty in the treatment of displaced femoral neck fractures: a prospective randomized study of 100 hips.

100 patients 75 years or older, with displaced femoral neck fractures, were randomly assigned to osteosynthesis with two parallel and percutaneously inserted screws (Olmed) or total hip arthroplasty (Lubinus IP). Mean age was 84 (75-101) years, 74% were women and 45% had mental dysfunction. General complications were commoner in the arthroplasty group but the mortality rates did not differ. In the osteosynthesis group, fracture complications were seen in 27/50 hips. In the arthroplasty group, dislocation was the main complication and occurred in 11/50 cases. At 3 months and after 1 year, the Harris Hip Scores were significantly better in the arthroplasty group. When mental dysfunction was present, the dislocation rate after arthroplasty was 32%, whereas the reoperation rate after osteosynthesis was 5%. The opposite pattern of complications was found in patients with normal mental function, 12% versus 60%. The 2-year mortality rate among those with mental dysfunction was 26/45, compared to 7/55 of those with normal function (p < 0.001). We conclude that total hip arthroplasty should be considered for a displaced femoral neck fracture in old patients with normal mental function and high functional demands.

Mild hypothermia does not increase blood loss during total hip arthroplasty.

BACKGROUND: The effects of mild hypothermia on blood loss are little known. METHODS: Patients, undergoing primary prosthetic hip surgery under spinal anaesthesia, were randomised to the operative procedure, with (n=25) or without (n=25) forced air warming. Core temperature was repeatedly measured from the tympanic membrane. The blood loss was calculated by three different methods; the intraoperative loss was estimated visually. The loss during and after the operation was obtained by determination of lost haemoglobin (the Hb-method). The blood loss during hospital stay was also calculated from the haemoglobin balance. RESULTS: Among controls, core temperature decreased by 1.3+/-0.6 degrees C (mean+/-SD) and in the warmed patients 0.5+/-0.4 degrees C (P<0.0001). Preoperative variables and the number of allogeneic units transfused did not differ between the groups. In controls, the blood loss during operation was, with the visual method, 698+/-314 ml, compared with 665+/-292 ml in warmed patients. With the Hb-method, the loss was 662+/-319 and 657+/-348 ml, respectively. With this method, the external loss during the entire hospital stay was, in controls, 1066+/-441 ml and in the warmed group, 1047+/-413 ml. The balance method yielded 1674+/-646 ml and 1507+/-652 ml, respectively. Indices of blood loss did not differ significantly between groups and there was no covariation between those variables and the decrease in core temperature. CONCLUSIONS: Forced air warming did not decrease the blood loss. Methods for determination of blood loss yielded widely differing results.

Intraoperative autotransfusion is associated with modest reduction of allogeneic transfusion in prosthetic hip surgery.

BACKGROUND: The efficacy of intraoperative salvage and washing of wound blood and the predictors of allogeneic red cell transfusions in prosthetic hip surgery are insufficiently known. METHODS: In 96 patients, undergoing primary or revision surgery, salvaged and washed red cells and, if necessary, allogeneic blood were used to keep haematocrit not lower than 33%. The bleeding of red cells during hospital stay was calculated from the red cell balance. The preoperative red cell reserve (mililitres of red cells in excess of a haematocrit of 33%) was estimated and the difference between this volume and the total bleeding of red cells was retrospectively used to classify patients with regard to the need for red cells. Stepwise regression analysis was used to define patient-related variables associated with allogeneic blood transfusion. RESULTS: Preoperative knowledge of the type of operation (primary, revision), the preoperative red cell reserve, and the body mass could predict roughly half of the need for banked blood (r2 = 0.45). Only one-third of the total bleeding of red cells was retransfused. For complete avoidance of allogeneic blood, autotransfusion was most effective in patients with a moderate need (0-4 u). However, 32% of such patients required allogeneic blood. CONCLUSIONS: Autotransfusion has a limited efficacy to decrease the need for allogeneic blood, and other blood-saving methods should be added for this purpose. It is difficult to predict the need for allogeneic blood preoperatively.

The structural basis of MHC control of collagen-induced arthritis; binding of the immunodominant type II collagen 256-270 glycopeptide to H-2Aq and H-2Ap molecules.

The Aq major histocompatibility complex (MHC) class II molecule is associated with susceptibility to murine collagen-induced arthritis (CIA), whereas the closely related H-2Ap molecule is not. To understand the molecular basis for this difference, we have analyzed the ability of H-2Aq and H-2Ap molecules (referred to as Aq and Ap) to bind and present collagen type II (CII)-derived glycosylated and non-glycosylated peptides. T cell clones specific for the immunodominant CII 256-270 peptide and restricted to both Aq and Ap molecules were identified. When these clones were incubated with CII protein and either Aq- or Ap-expressing antigen-presenting cells (APC), only Aq-expressing APC were able to induce stimulation. With the use of A(beta) transgenic mice this could be shown to be solely dependent on the MHC class II molecule itself and to be independent of other MHC- or non-MHC genes. Peptide binding studies were performed using affinity-purified MHC class II molecules. The CII 256-270 peptide bound with lower affinity to the Ap molecule than to the Aq molecule. Using a set of alanine-substituted CII 256-270 peptides, MHC class II and T cell receptor (TCR) contacts were identified. Mainly the side chains of isoleucine 260 and phenylalanine 263 were used for binding both the Aq and Ap molecule, i.e. the peptide was orientated similarly in the binding clefts. The major TCR contact amino acids were lysine 264, which can be posttranslationally modified, and glutamic acid 266, which is the only amino acid in the heterologous peptide which differs from the mouse sequence. Glycosylation at positions 264 and 270 of the CII 256-270 peptide did not change the anchor positions used for binding to the Aq or Ap molecules. The autologous form of the peptide (with aspartic acid at position 266) bound with lower affinity to the Aq molecule as compared with the heterologous peptide. The variable affinity displayed by the immunodominant CII 256-270 peptide for different MHC class II molecules, the identification of MHC and TCR contacts and the significance of glycosylation of these have important implications for the understanding of the molecular basis for inherited MHC class II-associated susceptibility to CIA and in turn, for development of novel treatment strategies in this disease.

Structural basis for the negative allostery between Ca(2+)- and Mg(2+)-binding in the intracellular Ca(2+)-receptor calbindin D9k.

The three-dimensional structures of the magnesium- and manganese-bound forms of calbindin D9k were determined to 1.6 A and 1.9 A resolution, respectively, using X-ray crystallography. These two structures are nearly identical but deviate significantly from both the calcium bound form and the metal ion-free (apo) form. The largest structural differences are seen in the C-terminal EF-hand, and involve changes in both metal ion coordination and helix packing. The N-terminal calcium binding site is not occupied by any metal ion in the magnesium and manganese structures, and shows little structural deviation from the apo and calcium bound forms. 1H-NMR and UV spectroscopic studies at physiological ion concentrations show that the C-terminal site of the protein is significantly populated by magnesium at resting cell calcium levels, and that there is a negative allosteric interaction between magnesium and calcium binding. Calcium binding was found to occur with positive cooperativity at physiological magnesium concentration.

Influence of temperature and vacuum mixing on bone cement properties.

To analyze the influence of varying viscosity and mixing temperature (22 degrees C and 6 degrees C) on macro- and microporosity, density, and compressive strength in vacuum mixed bone cement, high, medium, and low viscosity cement were mixed in 2 vacuum mixing systems and compared with bowl mixing at atmospheric pressure. At 22 degrees C, vacuum mixing significantly reduced void volume to less than approximately 3 per mill. The reduction was most pronounced in low viscosity cement. Microporosity also was reduced in all cements by vacuum mixing and to highest degree in low viscosity cement. At 6 degrees C the reduction of micropores was more pronounced in high viscosity cement. In medium and especially low viscosity cement, the prechilling gave an increased number of micropores. Cement density also was significantly reduced in low viscosity cement at 6 degrees C. Vacuum mixing significantly increased compressive strength by approximately 15% in all cement types (30 days). The temperature did not significantly influence compressive strength, but low viscosity cement generally was stronger when mixed at 22 degrees C. It is concluded that vacuum mixing improves cement quality. However, the temperature influences the final result; in particular, low viscosity cement should not be mixed after prechilling to 6 degrees C.

Giving both enoxaparin and dextran increases the need for transfusion in revision hip arthroplasty.

OBJECTIVE: To find out if the need for transfusion was increased by volume substitution with dextran 70 in patients receiving prophylaxis against thrombosis with low molecular weight heparin. DESIGN: Open randomised controlled trial. SETTING: University hospital, Sweden. SUBJECTS: 40 patients undergoing revision hip arthroplasty. INTERVENTIONS: Enoxaparin 40 mg was given daily. Intraoperative normovolaemia was maintained with albumin (n = 20) or dextran 70 (n = 20). Intraoperative autotransfusion was used. Packed cell volume was kept above 0.29, if necessary with homologous blood. MAIN OUTCOME MEASURES: External blood loss, red cell balance. RESULTS: Dextran patients received 0.64 (0.2) g/kg of dextran (mean (SD)) and required more (p < 0.05) homologous blood (3.8 (2.4) units) than those receiving albumin (2.3 (1.6) units). The initial and final packed cell volumes were similar (0.40 and 0.32 compared with 0.41 and 0.32, respectively). The calculated loss of red cells was larger in the dextran group (1401 (511) compared with 1077 (374); p < 0.05). CONCLUSION: The combination of enoxaparin and dextran appreciably increased the need for transfusion compared with enoxaparin alone.

Stem loosening more common with ITH than Lubinus prosthesis. A 5-year clinical and radiographic follow-up of 142 patients.

Out of a consecutive series of 169 cemented total hip arthroplasties, 77 Lubinus SP 2 and 65 ITH prostheses, were followed-up after 5 years with clinical and radiographic assessments. Radiolucencies were commoner around the ITH titanium stem than around the Lubinus cobalt-chrome stem. 6 of the ITH stems were considered as definitely loose, as compared to none of the Lubinus stems. Hitherto, 5 patients in the ITH group have had revisions and 2 need revision because of loosening. The poorer performance of the cemented ITH stem may be due to an unfavorable combination of design and material properties.

Effect of diclofenac on fixation of hydroxyapatite-coated implants. An experimental study.

We studied the effect of non-steroidal anti-inflammatory drugs on the fixation of hydroxyapatite-coated implants. Cylindrical plugs of pure titanium, coated with hydroxyapatite (HA), were inserted into both femora of 10 adult rabbits, 5 of which received 7 daily doses of 30 mg diclofenac. Three weeks after implantation the interface strengths were measured by the pull-out test. The mean peak force for the diclofenac-treated group was 290 +/- 57 N compared with 369 +/- 37 N for the control group (p < 0.025). We conclude that the inhibitory effect of diclofenac on bone repair is not neutralised by HA-coating of an implant.

Revision of infected hip replacement. Two-stage procedure with a temporary gentamicin spacer.

We revised 5 infected totally-replaced hips in 2 stages. At the first operation a gentamicin-loaded modelled cement spacer was inserted, and the definitive prosthesis was inserted 3-8 weeks later. 9-24 months after the last operation, there was a recurrent infection in 1 case. 2 of the patients could walk in the interval.

Design and testing of a flexible hip prosthesis.

A prosthesis with flexibility and optimal proximal fit was constructed in titanium alloy. The aim was to create the same elasticity as in the femoral shaft. Distally it was cylindrical with slots in the stem and a spacer made of polymer was placed in the slots. The proximal part of the prosthesis was wedge-shaped in both planes and a collar with a conical contact surface to bone was used. Pure titanium was plasma sprayed on the upper part as well as underneath the collar allowing bony ingrowth. A test jig was constructed and 10 million cycles with 4000 N loading was planned. The prosthesis broke after 600 000 cycles and it was a typical fatigue failure. A commercially available flexible prosthesis was tested as a reference and broke after 29 000 cycles. It is concluded that construction of a flexible hip prosthesis using metal with reasonable security against fatigue failure breakage is difficult, and we are somewhat doubtful if it is possible.

A prospective comparison of Butel and PCA hip arthroplasty.

We compared two cementless femoral components, the 'isoelastic' Butel stem and the more rigid PCA design, in a randomised, prospective study of 56 patients with a mean follow-up of 4 years (2 to 5). Patients were matched in 28 pairs, and one of each pair was treated with each femoral component. The isoelastic stem gave fewer signs of stress shielding radiologically, but both the Harris hip score and the visual analogue pain scale showed significantly inferior results at the two-year and three-year follow-up. The overall failure rates for the femoral components were 43% for the Butel and 11% for the PCA. These results contrast with those of earlier experimental and clinical studies, in which isoelastic properties appeared to be advantageous. This review emphasises the importance of controlled studies before an altered or new design of prosthesis is released on to the market for general use.

Renal function after hip arthroplasty and isoxazolylpenicillin prophylaxis.

Two different isoxazolylpenicillins (cloxacillin and dicloxacillin) were compared regarding impairment of renal function after total hip arthroplasty. 85 patients received dicloxacillin and 93 patients received cloxacillin as antibiotic prophylaxis. A total dose of 6 grams was given during a 36-hour period in doses of 1 gram pre-, per- and postoperatively. Creatinine in serum and beta 2-microglobulin in serum and urine were determined preoperatively and 2, 4, and 10 days after the operation. The dicloxacillin-treated patients had an increase in creatinine and beta 2-microglobulin in serum that was not seen in the cloxacillin group. The increase indicates a transient injury in the process of glomerular filtration. Although the increase was temporary and subclinical, a dose reduction is nevertheless recommended for older patients.

The strain distribution in the upper tibia after insertion of two different unicompartmental prostheses.

The strain distribution in the proximal tibia in seven human autopsy specimens was investigated with strain-gauge rosettes attached on the medial proximal aspect of the tibia. The strains measured were about the same on the proximal bone and on the bone in the metaphysis. The direction of the minimal principal strain (compression) was about 45 degrees counterclockwise (left knee). After insertion of a unicompartmental prosthesis medially, a non-constrained prosthesis with a loose meniscus-bearing and a constrained prosthesis, the tensile strain was about four times higher in the most anteromedial gauge. No significant differences were found between prostheses. Tests were also performed with the two prostheses inserted into three plastic models. The constrained prosthesis was more sensitive to outward rotation of tibia versus femur, which made the femoral component climb up the slope of the tibial component and caused a marked change in the strain distribution compared to loading in the neutral position. With the other prosthesis, a malpositioning of the tibial component medially caused the meniscus bearing to lie close to the medial rim of the tibial component. An external rotation of tibia then made the system constrained and dramatically changes the strain distribution.

Rehabilitation after high tibial osteotomy and unicompartmental arthroplasty. A comparative study.

Ten patients with medial gonarthrosis treated by unicompartmental arthroplasty were matched with ten patients who had high tibial osteotomy; their courses of rehabilitation were evaluated. All patients regained motion without problems, with no difference between the groups. Muscle torque was measured by a Cybex II dynamometer. The results six months postoperatively were better in the patients treated by unicompartmental arthroplasty than they were 12 months postoperatively in the patients treated by high tibial osteotomy. In the prosthesis group there was an increase in the maximal gait velocity and the duration of single support. In the osteotomy group there was no significant change. This difference in the results of rehabilitation constitutes an argument for arthroplasty in aged patients.

Knee rotation after unicompartmental arthroplasty.

Knee rotation was tested in twenty patients before and 6 months after unicompartmental replacement. Rotation during active extension was measured using a Genucom Knee Analysis System. From 90° of flexion the tibia normally rotates internally, followed by external rotation until full extension. Compared to 14 healthy control knees the internal rotation was about the same but the external rotation was less (P < 0.01). There was no difference between the pre- and postoperative measurements. Ten patients had replacement with a constrained prosthesis (PCA) and ten patients replacement with a non-constrained prosthesis (Oxford). There was no difference in rotation between the two prostheses. A possible explanation is that ligaments are more important in the restriction of rotation than is the shape of condyles. The extension lag in several knees was not found to be crucial.

High tibial osteotomy for medial osteoarthritis of the knee. A 5 to 7 and 11 year follow-up.

On three occasions we have reviewed a series of knees after high tibial osteotomy for osteoarthritis: 99 were reviewed at one to two years; 81 at a mean of 5.7 years; and 65 at a mean of 11.9 years. At one to two years and at 5.7 years over 50% were good and over 75% acceptable. At 11.9 years, 43% were good and 60% acceptable. We determined the mechanical axis through the knee in maximum varus and maximum valgus; significantly better results were found if a mean angulation of 3 degrees to 7 degrees of valgus had been achieved at operation. We also measured intercondylar distances under varus and valgus stress, and found no significant lateral compartment narrowing. The best results were seen in knees with pre-operative grade I or grade II osteoarthritis and valgus deviation after osteotomy.

Gait analysis in patients with gonarthrosis treated by high tibial osteotomy.

The basic parameters of gait were studied in 14 patients with medial gonarthrosis before and eight to 12 months after high tibial osteotomy. In seven patients, the osteotomy was fixed with staples. The patient was placed in plaster immobilization for six weeks and weight bearing was allowed after ten weeks. In the other seven patients, the osteotomy was fixed with a T-plate, and immediate joint motion and weight bearing were allowed after six weeks. There was no difference in any parameter of gait among patients treated with the two techniques. For all patients, the mean maximal velocity preoperatively was 65% of that of normal people, with only a slight, nonsignificant increase at the follow-up examination. An additional indication of insufficient rehabilitation was the decrease in stride length at constant maximal velocity at the follow-up evaluation. Positive correlations were found between stride length and muscle torque in the thigh. Positive correlations were also found between a subjective score and maximal velocity. Simple tests of velocity, stride length, and stride frequency are recommended as an easy and decisive method of follow-up evaluation.

The effect of the radiographic projection on the measured position of the prosthesis at knee arthroplasty.

Radiographic pictures with different centerings were taken of a Geomedic prosthesis attached to a knee joint preparation. Moderate rotations and incorrect centerings did not result in significantly different measurements.