Periprosthetic Stress Fractures at the Sleeve/Stem Junction of the Sivash-Range of Motion Modular Femoral Stem

We report on 13 cases of periprosthetic stress fracture at the sleeve/stem junction using the Sivash-Range of Motion femoral prosthesis. Radioisotope bone scans confirmed the incidence of fracture, and review of the lateral radiographs revealed anteromedial notching of the distal sleeve on the metaphyseal throat of the femur. Treatment in all cases was expectant with full resolution of symptoms. However, there were 3 cases of recurrence, 1 of which needed revision to a more distally loading stem. This is a rare complication when using this prosthesis, but we recommend a slight alteration of the entry point for the femoral reamer when using this stem and advise nonsurgical management if it occurs, as the natural history is for the condition to settle.     

Regional differences in cortical bone mineral density in the weight-bearing long bone shaft--a pQCT study

This study used a multislice peripheral quantitative computed tomography (pQCT) to measure volumetric BMD (vBMD) and cortical thickness for investigating regional adaptation in lower tibial shaft in 72 healthy postmenopausal women aged 47-60. Tomographic slices were analysed on four distinct cortical regions: the anterior, posterior, medial and lateral cortical wall. One-way analysis of variance (ANOVA) test was used to compare the vBMD in the four regions. The results showed that the posterior cortex had the highest vBMD (1923 +/- 135.3 mg/cm(3)), significantly (P < 0.001) higher than the anterior cortex (1805 +/- 110.6 mg/cm(3)), medial cortex (1863 +/- 103.6 mg/cm(3)) and lateral cortex (1815 +/- 111.6 mg/cm(3)); whereas there was no significant difference (P > 0.05) between the medial and lateral cortices located near the neutral plane of bending. The anterior cortex had the greatest thickness (2.56 +/- 0.47 mm), significantly (P < 0.001) greater than that of the posterior cortex (2.11 +/- 0.27 mm), medial cortex (2.20 +/- 0.39 mm) and lateral cortex (2.03 +/- 0.29 mm). The vBMD of the posterior cortex was a significant 6.5% higher than that of the anterior cortex (P < 0.001); whereas the anterior cortical thickness was a significant 21.3% greater than that of the posterior cortex (P < 0.001). There was no linear relationship found between cortical vBMD and cortical thickness measured at the four cortical regions (r = 0.086, P > 0.05). In conclusion, the regional differences, with higher vBMD found in posterior cortex, might be a result of mechanical adaptation, which caused the posterior cortex to sustain higher compressive loading than the anterior tensile cortex during the landing phase in the gait cycles of individuals. Nevertheless, regional geometric adaptation in anterior cortical thickness might be adapted to accommodate for the reduced vBMD and to reduce the bending stress in this region.     

Results of a hydroxyapatite-coated modular femoral stem in primary total hip arthroplasty. A minimum 5-year follow-up

The use of a modular metaphyseal-diaphyseal femoral stem in primary total hip arthroplasty is infrequent. We analyze 94 ESOP (Fournitures Hospitalieres, Heimsbrunn, France) cementless 2-piece modular stems after a minimum 5 years of follow-up. There were 2 aseptic femoral stem loosenings and no cases with thigh pain. Mean femoral canal filling was 90%. Radiographic ingrowth was obtained in 83 (P < .001). At 7 years, the survival rate for femoral aseptic loosening was 97.8% and no stem was at risk for revision (95% confidence interval, 94.8%-100%). This prosthesis provides good clinical results with absence of pain and excellent radiographic results. It is an option in femora with good bone quality. Femoral osteopenia and cortical widening were infrequent, and the modular metaphyseal-diaphyseal junction was not a problem in vivo.     

Migration of the Femoral Stem in Hip Arthroplasties: Analysis of Associations with Structural,Radiological and Follow-up Variables

Medial and/or distal migration of the prosthetic stem was found in 63 out of 337 patients (19 per cent) treated surgically with a Christiansen hemiprosthesis, a Christiansen total hip prosthesis or a Charnley total hip prosthesis.

Fractured bone cement, radiolucent zones at the cement/bone interface, resorption of the femoral calcar and cortical sclerosis were all associated with migration. Varus position of the Christiansen total hip prosthesis was significantly associated with medial migration, and a short stem was significantly associated with distal migration. The other structural variables could not be linked with migration. Distal migration was pain-inducing and was significantly associated with late infection. Medial migration had a less distinct association with pain, and was not correlated with infection. Both medial and distal migration were time-dependent, and 4 or more years after operation about 25 per cent of the prosthetic stems had migrated.     

Mechanical stress on the osseous tibial plateau in complement joint surface replacement--a finite element analysis]

For an unconstrained bicondylar sledge knee prosthesis the mechanical load of the bony support is crucial. For a design of a tibial component of such a prosthesis with improved anatomical features allowing a complete cortical support of the rim of the prosthesis, a finite element study was performed. Stress reactions of the bone for different implantation modes were calculated. Irrespective of the bony support of the prosthesis, tensile stresses are always transferred at the interface prosthesis/bone into the bone. For a complete cortical support of the rim of prosthesis, the areas of tensile stress in the bone are closely related to areas of high compression stress. If there is cortical support of the prosthesis only on the medial side due to an undersized prosthesis, this is only of minor influence on the stress pattern in the bone. However, if there is cortical support of the prosthesis only on the lateral side, there are large areas of tensile stresses in the lateral compartment of the tibial plateau. However, tensile stress transfer in the tibial plateau must be regarded as unphysiologic and therefore unfavourable. Therefore, if intraoperatively complete cortical support of the prosthesis cannot be achieved a more medial cortical support of such a prosthesis should be preferred to a lateral cortical support.     

Influence of cement viscosity and cement mantle thickness on migration of the Exeter total hip prosthesis

The effect of bone cement viscosity and cement mantle thickness on the migration of the Exeter total hip prosthesis was studied in a prospective, randomized, double-blind clinical Roentgen Stereophotogrammetric Analysis study. Forty-one cemented total hip arthroplasty in 39 patients were included and randomized into a low/medium Simplex P cement group and a high-viscosity Simplex AF cement group. At time of stem introduction, 5 minutes after mixing, the Simplex AF was more viscous than Simplex P. No statistical difference existed between the 2 cement groups, for neither translation nor rotation migration data. Subsidence of the stem at 2-year follow-up was 1.1 +/- 0.56 mm for Simplex AF cement and 1.5 +/- 1.00 mm for Simplex P cement. The mean rotation of the acetabular components about the sagittal axis was 1.7 degrees +/- 3.8 degrees in the Simplex AF group and 0.7 degrees +/- 2.1 degrees for the Simplex P group. No effect of cement mantle thickness on migration of neither the acetabular cups nor the femoral stems was found. Although there were no differences in migration data for the cups and the stems, 2 acetabular cups in the Simplex AF group (almost 10%) were revised because of mechanical loosening. Because of these findings, we suggest caution before using this new high-viscosity bone cement for fixation of acetabular components.     

从骨溶解的X线特征探讨磨损颗粒与人工髋关节无菌性松动的关系

目的 探讨自人工关节关节面首产生的磨损颗凿的迁移途径及其易素积部位与骨溶解之间的。方法 观察因无菌性松动行翻修术的３９个国产人工髋关节的术前Ｘ线片,按关节类型分组统计假体周围不同区域补性和膨胀发现有溶解的发生经,并测算溶骨带宽度或溶骨面积。结果 髋臼衬性骨溶解的发和率各区差异无显著性意义（Ｐ〉０．０５）,宽度以三区（Ｄｅｌｅｃ分区法）最大（Ｐ〈０．０５）;膨胀发现有溶解在人工股骨头和全髋关节中髋臼     

Total hip replacement with a trunnion bearing prosthesis. Biomechanical principles and preliminary clinical results.

The biomechanics are presented of a bushing principle forming the basis for a trunnion bearing prosthesis in total hip replacement. The femoral stem is equipped with a trunnion on to which a cylindrical plastic sleeve is applied. On top of this a metal casing is placed which forms the femoral head. On flexion-extension this remains stationary in the acetabular cup and motion occurs between the trunnion and the cylindrical sleeve. Friction between head and cup is reduced to a minimum, decreasing the risk of loosening. A follow-up study of 61 hips replaced by the trunnion bearing prosthesis was performed 2.5 years postoperatively. Eighty-eight per cent were considerably improved. There was one deep infection and two femoral stem loosenings.     

Total Hip Replacement with a Trunnion Bearing Prosthesis: Biomechanical Principles and Preliminary Clinical Results

The biomechanics are presented of a bushing principle forming the basis for a trunnion bearing prosthesis in total hip replacement. The femoral stem is equipped with a trunnion on to which a cylindrical plastic sleeve is applied. On top of this a metal casing is placed which forms the femoral head. On flexion-extension this remains stationary in the acetabular cup and motion occurs between the trunnion and the cylindrical sleeve. Friction between head and cup is reduced to a minimum, decreasing the risk of loosening.

A follow-up study of 61 hips replaced by the trunnion bearing prosthesis was performed 2.5 years postoperatively. Eighty-eight per cent were considerably improved. There was one deep infection and two femoral stem loosenings.     

Failed Christiansen total hip arthroplasty. A radiographic and histologic study

Twenty-two consecutive cases of the Christiansen total hip arthroplasty revised because of aseptic loosening were analyzed with regard to radiographic changes and operative and histopathologic findings. This prosthesis was designed with a socket and a trunnion sleeve made of polyoxymethylene or Delrin. In 18 cases there was isolated socket loosening, in all cases there was obvious bone resorption beneath the collar of the stem, and in 20 cases the socket had migrated. The radiographic socket wear rate averaged 0.4 mm/year. In 18 cases a significant amount of debris material was found in the joint cavity. Light microscopy revealed a severe foreign body reaction with numerous plastic particles, most often engulfed by macrophages. Taken together, these findings indicate that socket wear leading to a foreign body reaction with bone resorption is the main cause of the poor results noted with this particular total hip prosthesis.     

Measurement of bone mineral density by dual-energy X-ray absorptiometry around an uncemented knee prosthesis

Dual-energy x-ray absorptiometry allows the measurement of bone mineral density (BMD) around an uncemented hip prosthesis, but has not so far been widely used to measure BMD around a knee prosthesis. We studied 16 patients undergoing total knee replacement using a Miller-Galante uncemented prosthesis for either osteoarthritis or rheumatoid arthritis of the knee. The precision of the measurement was improved by using a leg brace. The pattern of bone loss differed in the lateral projection by region (P = .001). There was significant loss of bone from the distal femur but not from the patella or proximal tibia over the 6-month period after insertion of a knee prosthesis.     

Femoral cortical sleeve in revision arthroplasty 24 patients followed 2-10 years

22 women and 2 men with a mean age of 75 (51-90) years underwent replacement of the proximal femur for failed total hip arthroplasty by a modular femoral resection endoprosthesis (KMFTR). the indications were bone loss in aseptic loosening (n 8), fracture (n 12) and Girdlestone hips (n 4). After a mean follow-up of 5 (2-10) years, the Harris Hip Score improved from an average of 17 (4-43) to 79 (50-97). in 19 patients, the proximal femur was kept as an autograft and was wrapped around the resection parts of the modular prosthesis as a cortical sleeve. Bone forma tion in these 19 hips took place in 18 at the dorsal, in 17 at the medial, in 8 at the lateral and in 7 at the ventral aspect of the femur. the bone bridge formed within the first year and persisted in amount and distribution during the time of observation.

In the 5 patients without a remaining cortical sleeve around the resection parts of the prosthesis, no bone bridge was formed. These 5 patients showed stress-shielding at the prosthesis-bone-junction. Until now, none of the 24 patients has undergone additional surgery.     

Clinical and finite element analysis of a modular femoral prosthesis consisting of a head and stem component in the treatment of pertrochanteric fractures

OBJECTIVE: To determine the biomechanical characteristics and potential clinical efficacy of a cementless modular femoral prosthesis consisting of a variable head (50 to 80 millimeters) and stem (length 120 to 280 millimeters, diameter 10 to 20 millimeters) component in patients with pertrochanteric femoral fracture. DESIGN: Finite element analysis (FEA) of different lengths and diameters of prosthesis components and first clinical prospective study in pertrochanteric femoral fracture. METHOD: Using a 3D-CAD program, a model of femoral cortical bone with a pertrochanteric fracture was created and combined with a model of the prosthesis. This model was transferred into an FEA program. After applying a torsion-bending load of 2,000 N (25 degrees, 45 degrees) on the prosthesis, stress distribution in the cortical bone was determined for different lengths (160 to 240 millimeters) and diameters (10 and 12 millimeters) of stem. PATIENTS: Twenty-eight patients with pertrochanteric fractures (very unstable or osteoarthritis) were treated with a modular hip arthroplasty. Complications, fracture healing, and results at first follow-up (average 13 months) were determined. RESULTS: FEA analysis indicated that reduction in stress was less when a prosthesis with a short stem was used. Shear stress in the interface bone/prosthesis was not affected by stem length. Prostheses with thin stems produced higher sheer stresses than those with thick stems. Results of FEA were used as the basis for clinical application of the device. None of the patients died, and all patients were able to walk, although some needed a cane or walker after surgery. There was no increase in thigh pain compared with reported pretrauma levels. Radiographs showed subsidence of up to 5 millimeters in 20 percent of patients. However, all but one prosthesis was stable at follow-up. Fracture healing was achieved in all patients. CONCLUSIONS: If proximal fixation of a femoral uncemented stem cannot be achieved, stem diameter should provide maximum cortical contact to reduce sheer stress. Longer stems do not necessarily provide additional stability. By using this prosthesis and selection method, a good outcome at first follow-up was observed.     

Salvage of failed hinge knee arthroplasty with a Total Condylar III type prosthesis

Fourteen failed aseptic-hinge total-knee arthroplasties (TKA) were reviewed to determine if an unlinked metal to plastic Total Condylar III type prosthesis can be used for salvage procedure. The overall preoperative Hospital for Special Surgery knee-rating score was 58 and improved to 81 post-operatively. The average postrevision range of motion was 83 degrees. The soft tissue sleeve, the built-in constraint of the prosthesis, and the restoration of the bone deficiency provided good stability, despite the loss of the collateral and cruciate ligaments. Radiolucent lines, less than 1 mm in width and incomplete, appeared in four femoral and ten tibial bone-cement interfaces. In one femoral component there was a 2-mm radiolucency with a cement fracture at the femoral stem tip. There were no failures or repeated revisions, but two knees required postoperative manipulation to improve motion. Total Condylar III type prosthesis can be satisfactorily used to salvage failed hinge TKA.     

Primary hemiarthroplasty in four-part fractures of the proximal humerus: randomized trial of two different implant systems

The objective of this study was to determine the effect of different prosthetic systems on the functional and radiographic outcomes after shoulder arthroplasty for fractures. This study comprised 35 patients (28 women and 7 men) with a mean age of 74 years (range, 56-88 years) who sustained 4-part fractures of the proximal humerus and were randomly allocated to 2 different groups regarding the type of prosthesis. The 2 systems used differ mainly in the type of fixation of the tuberosities. In group 1 (EPOCA), the fixation was achieved with wire cables through a medial and a lateral hole in the stem, whereas in group 2 (HAS), the fixation was performed by use of transosseous braided sutures. After a follow-up of 1 year, the functional and radiographic outcomes were evaluated. The retrieved data demonstrate that rigid fixation and anatomic positioning of the tuberosities (group 1) increase the rate of bony healing superior to all other factors. There was a statistically significant difference regarding the relative individual Constant score (P = .001) and the mean active range of motion (flexion, P < .001; abduction, P = .001; external rotation in adduction, P = .01; and external rotation in 90 degrees abduction, P = .001) when both groups were compared, showing a better outcome in the EPOCA group for all parameters. Radiologic findings, like heterotopic ossification, glenoid erosion, or subluxation, had no significant influence on the outcome in this study. Accurate placement of the tuberosities and healing at the bone-bone interface of the rotator cuff seem to be the most important factors influencing the outcome in prosthetic care of fractures.     

Treatment of a Well-Fixed Modular Fully Porous Coated Stem After Fracture Using a Custom Rescue Sleeve

We report a novel technique for the treatment of a fractured fully porous-coated modular stem. The fracture of the stem occurred at the taper of the stem-body junction. In both cases, the stem was well-fixed distally making the reconstruction difficult. Previously, authors have reported the use of an extended trochanteric osteotomy or multiple cortical windows for removal of this type of prosthesis. The technique we describe uses a custom-made “rescue sleeve” that takes advantage of the distal ingrowth. The rescue sleeve is fitted onto the existing stem obviating the need for an extended trochanteric osteotomy. The rescue sleeve's geometry makes up for the loss in height and accepts the modular body components to give the surgeon the length options to optimize stability.     

Total condylar III knee prosthesis. Long-term follow-up study

The total condylar III knee prosthesis (TCP III) is a constrained, unlinked knee that provides medial and lateral stability through a rectangular tibial post and a high femoral box. Thirty-one knees were implanted in 25 patients. There were 17 primary arthroplasties and 14 revisions. The average follow-up period was 3.8 years. The average arc of motion was improved from 63 degrees to 97 degrees. This resulted in 77% good and excellent results. There were five failures (16%), all of which occurred in the revision group. These results compare favorably with results of constrained prostheses; however, the deformity in this group was quite severe. The major indications for use of TCP III would be medial ligament loss, severe valgus or combined deformities, or cases of unstable revision in which a surface arthroplasty will not suffice. The prosthesis should not be used in cases that demonstrate massive bone loss. In those cases, the prosthesis should have a weight-bearing intramedullary stem to transfer stress lines to cortical bone.     

Evaluation of cortical bone by peripheral quantitative computed tomography in renal transplant recipients

BACKGROUND: The absolute risk of fractures in renal transplant patients is 3 times that of matched controls. Most of the symptomatic fractures are peripheral, suggesting a greater compromise of cortical bone. Peripheral quantitative computed tomography (pQCT) is a new imaging technique that allows separate noninvasive evaluations of cortical and trabecular bones. We investigated cortical bone by pQCT in 12 renal transplant patients (seven men and five women) for comparison with 27 normal controls. METHODS: pQCT (XCT 960, Stratec, Pforheim, Germany) was performed upon the distal radius of the nondominant forearm (15% the length of the ulna, proximal from the radius end plate). We evaluated total and cortical bone mineral density (TBMD, cBMD), total (cross-sectional) and cortical area (TA, cA), cortical thickness (cThk), endosteal and periosteal circumferences, and the buckling ratio (r/cThK). RESULTS: Compared with normal controls transplant patients as a whole showed a significant increase in TA, in endosteal circumference (P < .001), and in the buckling ratio (P < .001) with a significant reduction in cThK (P < .001). Female patients had a marked decrease in cA (51.4 vs 69.3 [pixel n]; P < .0001) and cThK (2.08 vs 2.78 mm; P < .0001). Male patients also had a decrease in cThK (2.54 vs 3.30 mm; P = .0001) and an increase in endosteal perimeter (31.2 vs 26.4 mm; P < .0001). Total time on dialysis prior to renal graft correlated negatively with cortical thickness (r = .62; P < .01). CONCLUSIONS: Our results suggest that a marked thinning of cortical bone may explain the increased incidence of peripheral fractures among renal transplant patients.     

Biomechanics of a short stem: In vitro primary stability and stress shielding of a conservative cementless hip stem

Short stem prostheses provide conservative surgery and favorable metaphyseal load transmission. However, clinical long‐term results are lacking. Therefore, in vitro trials can be used to predict bone‐implant performance. In this in vitro study, primary stability and stress shielding of a new cementless short stem implant was evaluated in comparison to a straight stem using nine pairs of human cadaver femurs. Primary stability, including reversible micromotion and irreversible migration, was assessed in a hip simulator. Furthermore, changes in the pattern of cortical strain were evaluated. The short stem was more resistant to reversible micromotion and irreversible migration into retroversion. Axial stability was similar, with mean reversible micromotions of 9 µm for the short stem and 7 µm for the straight stem. Proximal load transmission was more physiological with the short stem, though both implants could not avoid stress shielding in Gruen zones 1 and 7. Primary stability of the short stem prosthesis was not negatively influenced compared to the straight shaft. Furthermore, proximal femoral strain pattern was more physiological after insertion of the short stem prosthesis. (c) 2013 Orthopaedic Research Society Published by Wiley Periodicals, Inc. J Orthop Res 31:1180–1186, 2013     

Stress-shielding of the proximal femur using an extensively porous-coated femoral component without allograft in revision surgery: a 5- to 17-year follow-up study

Revision surgery of the hip was performed on 114 hips using an extensively porous-coated femoral component. Of these, 95 hips (94 patients) had a mean follow-up of 10.2 years (5 to 17). No cortical struts were used and the cortical index and the femoral cortical width were measured at different levels. There were two revisions for aseptic loosening. Survivorship at 12 years for all causes of failure was 96.9% (95% confidence interval 93.5 to 100) in the best-case scenario. Fibrous or unstable fixation was associated with major bone defects. The cortical index (p = 0.045) and the lateral cortical thickness (p = 0.008) decreased at the proximal level over time while the medial cortex increased (p = 0.001) at the proximal and distal levels. An increase in the proximal medial cortex was found in patients with an extended transtrochanteric osteotomy (p = 0.026) and in those with components shorter than 25 cm (p = 0.008). The use of the extensively porous-coated femoral component can provide a solution for difficult cases in revision surgery. Radiological bony ingrowth is common. Although without clinical relevance at the end of follow-up, the thickness of the medial femoral cortex often increased while that of the lateral cortex decreased. In cases in which a shorter component was used and in those undertaken using an extended trochanteric osteotomy, there was a greater increase in thickness of the femoral cortex over time.