Background. Spondylolysis (SL) of the lower lumbar spine is frequently associated with spina bifida occulta (SBO). There has not been any study that has demonstrated biomechanical or genetic predispositions to explain the coexistence of these two pathologies. Purpose. To test the hypothesis that fatigue failure limits will be exceeded in the case of a bifid arch, but not in the intact case, when the segment is subjected to complex loading corresponding to normal sporting activities. Methods. Finite element models of natural and SBO (L4-S1) including ligaments were loaded axially to 1kN and were combined with axial rotation of 3°. Bilateral stresses, alternating stresses and shear fatigue failure on intact and SBO L5 isthmus were assessed and compared. Results. Under 1kN axial load, the von Mises stresses observed in SBO and in the intact cases were very similar (differences < 5MPa) having a maximum at the ventral end of the isthmus that decreases monotonically to the dorsal end. However, under 1kN axial load and rotation, the maximum von Mises stresses observed in the ipsilateral L5 isthmus in the SBO case (31MPa) was much higher than the intact case (24.2MPa) indicating a lack of load sharing across the vertebral arch in SBO. When assessing the equivalent alternating shear stress amplitude, this was found to be 22.6 MPa for the SBO case and 13.6 MPa for the intact case. From this it is estimated that shear fatigue failure will occur in less than 70,000 cycles, under repetitive axial load & rotation conditions in the SBO case, while for the intact case, fatigue failure will occur only after more than 10 million cycles. Conclusion. SBO predisposes SL by generating increased stresses across the inferior isthmus of the inferior articular process, specifically in combined axial rotation and anteroposterior shear

Revision of the failed femoral component can be challenging. Multiple reconstructive options are available and the procedure is technically difficult and thus meticulous pre-operative planning is required. The Paprosky Femoral Classification is useful as it helps the surgeon determine what bone stock is available for fixation and hence, which type of femoral reconstruction is most appropriate. Type 1 Defect: This is essentially a normal femur and reconstruction can proceed as the surgeon would with a primary femur. Type 2 Defect: The metaphysis is damaged but still supportive and hence a stem that gains primary fixation in the metaphysis can be used. Type 3 Defect: The metaphysis is damaged and non-supportive and hence a stem that gains primary fixation in the diaphysis is required. Broken down into types “A” and “B” based on the amount of intact isthmus available for distal fixation. Type 3A Defect: >4 cm of intact femoral isthmus is present. Can be managed with a fully porous coated stem, so long as the diameter is <18 mm and torsional remodeling is not present. Type 3B Defect: There is < 4 cm of intact femoral isthmus and based on lower rates of osseointegration if a fully porous coated stem is used, a modular titanium tapered stem is recommended. Type 4 Defect: The most challenging to manage as there is no isthmus available for distal fixation. Can be managed with proximal femoral replacement if uncontained and impaction grafting if contained. We have also successfully used modular titanium tapered stems that appear to gain “3-point fixation” in this type of defect

Background. The purpose of this study was to investigate the morphology characteristic of proximal femur of Chinese people. 170 healthy Southern Chinese hips being measured using 3D computer tomographic, in order to improve prosthesis design and preoperation plan of total hip arthroplasty. Methods. This study measured proximal femoral geometry in 85 healthy Southern Chinese, included 39 women (78 hips) and 46 men (92 hips) (mean age: 33.9 y, mean height: 164.7 cm, mean weight 59.9 kg). Medullary canal morphology measurements, include: the position of isthmus, medial-lateral(ML) and anteroposterior(AP) medullary canal diameter of isthmus and 20 mm, 10 mm, 0 mm, −20 mm, −160 mm, −200 mm upon less trochanter(LT) (medullary canal height, MCH), canal flare index(CFI), aspect ratio(ML/AP), epiphysis-shaft angel (ES angel) (a posterior bow in the metapysis in lateral view). Exterior morphology measurements include: femoral head offset, ML and UD diameter, femoral head position(FHP) from LT, height of the femoral head center from the tip of the great trochanter(GT)(FHCH), femoral neck and head anteversion angle, femoral neck-shaft angle, neck length, neck width, intertrochanteric length (Fig 1, Fig 2). And then we use student's t–test to compare means, linear regression and correlation to analysis these data's relationship, p value <0.05 indicated a significant effect. Results. Males had a larger diameter of medullary canal than females (Fig3). The isthmus position is 117.69±11.95 VS 111.14±13.01 mm (male VS female) (p=0.070) below less trochanter, and it's ML diameter is 9.57±1.52 VS 8.88±1.80 mm (p=0.151), AP diameter is 11.85±2.68 VS 10.53±2.49 mm (p=0.073). The mean medullary canal aspect ratio is 1.38±0.20, 1.30±0.12, 1.15±0.13, 1.03±0.09, 0.84±0.11, 0.87±.011 and 1.04±0.17 respectively at 20 mm, 10 mm, 0 mm, −20 mm, isthmus, −160 mm, −200 mm upon less trochanter. The medullary canal diameter were positively correlated to MCH (R=0.793, p=0.000 VS R=0.790, p=0.000) (ML VS AP). The ES angle is 156.78±4.29 VS 157.90±4.90 degree (p=0.395) (male VS female). The femoral head offset is 39.14±3.87 VS 35.86±3.68 mm (p=0.003), femoral neck, head and comprehensive anteversion angle is 18.34±8.07 VS 17.9±10.64 degree (p=0.872), −2.61±6.47 VS −2.36±5.55 degree (p=0.881) and 15.73±7.26 VS 15.54±8.54 degree (p=0.934). FHP is 51.67±7.82 VS 45.37±5.59 mm (p=0.001), FHCH is −6.77±5.58 VS −6.13±4.87 mm (p=0.665), femoral head diameter is (ML: 43.94±2.62 VS 39.25±2.66 mm (p=0.000), UD: 45.16±1.96 VS 41.26±2.23 mm (p=0.000)). Femoral neck-shaft is 130.10±4.57 VS 130.83±6.40 degree (p=0.652), femoral neck length and width is 21.84±4.87 VS 20.69±3.41 mm (p=0.322) and 34.75±2.26 VS 31.80±2.63 mm (p=0.000), femoral intertrochanteric length is 68.11±4.72 VS 61.27±5.04 mm (p=0.000), most of these dimensions were positively correlated to height. Conclusion. Males had a larger medullary canal than females, the long diameter of medullary canal is transverse at proximal femoral, and it gradually become longitudinal when move to isthmus then become transverse again below isthmus, this may offer valuable revelation for our anti-rotation design and better distal fixation. The medullary canal diameter were positively correlated to MCH. 71% (121 hips) femoral heads had a retroversion angle compare to femoral neck. The femoral head rotation center is below the tip of the GT rather than on the same level that may suggested a shorter neck implants for Southern Chinese patients

As the number of patients who have undergone total hip arthroplasty rises, the number of patients who require surgery for a failed total hip arthroplasty is also increasing. It is estimated that 183,000 total hip replacements were performed in the United States in the year 2000 and that 31,000 of these (17%) were revision procedures. Reconstruction of the failed femoral component in revision total hip arthroplasty can be challenging from a technical perspective and in pre-operative planning. With multiple reconstructive options available, it is helpful to have a classification system which guides the surgeon in selecting the appropriate method of reconstruction. A classification of femoral deficiency has been developed and an algorithmic approach to femoral reconstruction is presented. Type I:. Minimal loss of metaphyseal cancellous bone with an intact diaphysis. Often seen when conversion of a cementless femoral component without biological ingrowth surface requires revision. Type II: Extensive loss of metaphyseal cancellous bone with an intact diaphysis. Often encountered after the removal of a cemented femoral component. Type IIIA: The metaphysis is severely damaged and non-supportive with more than 4cm of intact diaphyseal bone for distal fixation. This type of defect is commonly seen after removal of grossly loose femoral components inserted with first generation cementing techniques. Type IIIB: The metaphysis is severely damaged and non-supportive with less than 4cm of diaphyseal bone available for distal fixation. This type of defect is often seen following failure of a cemented femoral component that was inserted with a cement restrictor and cementless femoral components associated with significant distal osteolysis. Type IV: Extensive meta-diaphyseal damage in conjunction with a widened femoral canal. The isthmus is non-supportive. An extensively coated, diaphyseal filling component reliable achieves successful fixation in the majority of revision femurs. The surgical technique is straightforward and we continue to use this type of device in the majority of our revision total hip arthroplasties. However, in the severely damaged femur (Type IIIB and Type IV), other reconstructive options may provide improved results. Type IIIB:. Based on the poor results obtained with a cylindrical, extensively porous coated implant (with 4 of 8 reconstructions failing), our preference is a modular, cementless, tapered stem with flutes for obtaining rotational stability. Excellent results have been reported with this type of implant and by virtue of its tapered design, excellent initial axial stability can be obtained even in femurs with a very short isthmus. Subsidence has been reported as a potential problem with this type of implant and they can be difficult to insert. However, with the addition of modularity to many systems that employ this concept of fixation, improved stability can be obtained by impaction of the femoral component as far distally as needed while then building up the proximal segment to restore appropriate leg length. Type IV:. The isthmus is completely non-supportive and the femoral canal is widened. Cementless fixation cannot be reliably used in our experience, as it is difficult to obtain adequate initial implant stability that is required for osseointegration. Reconstruction can be performed with impaction grafting if the cortical tube of the proximal femur is intact. However, this technique can be technically difficult to perform, time consuming and costly given the amount of bone graft that is often required. Although implant subsidence and peri-prosthetic fractures (both intra-operatively and post-operatively) have been associated with this technique, it can provide an excellent solution for the difficult revision femur where cementless fixation cannot be utilised. Alternatively, an allograft-prosthesis composite can be utilised for younger patients in an attempt to reconstitute bone stock and a proximal femoral replacing endoprosthesis used for more elderly patients

Objective. To three-dimensionally reconstruct the proximal femur of DDH (Developmental dysplasia of the hip) and measure the related anatomic parameters, so that we could have a further understanding of the morphological variation of the proximal femur of DDH, which would help in the preoperative planning and prosthesis design specific for DDH. Methods. From Jan.2012 to Dec.2014, 38 patients (47 hips) of DDH were admitted and 30 volunteers (30 hips) were selected as controls. All hips from both groups were examined by CT scan and radiographs. The Crowe classification method was applied. The CT data were imported into Mimics 17.0. The three-dimensional models of the proximal femur were then reconstructed, and the following parameters were measured: neck-shaft angle, neck length, offset, height of the centre of femoral head, height of the isthmus, height of greater trochanter, the medullary canal diameter of isthmus(Di), the medullary canal diameter 10mm above the apex of the lesser trochanter(DT+10), the medullary canal diameter 20mm below the apex of the lesser trochanter(DT-20), and then DT+10/Di, DT-20/Di and DT+10/DT-20 were calculated. Results. There is no significant difference in neck-shaft angle between Crowe I-III DDH and the control group, while the neck-shaft angle is much smaller in Crowe IV DDH. The neck length of Crowe IV DDH is much smaller than those of Crowe I-III DDH. As for Di there is neither significant difference between Crowe I DDH and the control group, nor significant difference between CroweII-III and Crowe IV, but the difference is significant between the first two groups and the latter two groups. DT+10/DT-20 and the offset have no significant difference between the control group and DDH groups. DT-20, DT+10, DT+10/Di and DT-20/Di are much smaller in Crowe IV DDH than that in Crowe I-III and the control groups. Height of greater trochanter in Crowe IV is larger than those in Crowe I-III and the control group. Height of the centre of femoral head in Crowe IV DDH is smaller than those in Crowe I-III DDH and the control group. The height of the isthmus in Crowe IV is much smaller than those in Crowe I-III DDH and the control group. Conclusion. The neck-shaft angle in DDH groups is not larger than that in the control group, while in contrast, it's much smaller in Crowe IV DDH than that in the control group. Comparing to Crowe I-III DDH and the control group, Crowe IV DDH has a dramatic change in the intramedullary and extramedullary parameters. The isthmus and the great trochanter are higher and there is apparent narrowing of the medullary canal around the level of the lesser trochanter

Revision of the failed femoral component of a total hip arthroplasty can be challenging. Multiple reconstructive options are available and the operation itself can be particularly difficult and thus meticulous preoperative planning is required to pick the right “tool” for the case at hand. The Paprosky Femoral Classification is useful as it helps the surgeon determine what bone stock is available for fixation and hence, which type of femoral reconstruction is most appropriate. Monoblock, fully porous coated diaphyseal engaging femoral components are the “work-horse” of femoral revision. This type of a stem is used in my practice for Type 1–3a femoral defects. These stems are not used, however, in the following situations: The canal diameter is greater than 18mm; There is less than 4cm available for distal fixation in the isthmus; There is proximal femoral remodeling into retroversion. While many surgeons often believe that revision femoral components need to be “long”, they really only need to be long enough to engage 4cm of intact femoral isthmus, which is oftentimes the shortest, “primary length” fully porous coated stem. Advantages of using a shorter revision stem include: Easier surgical technique as you avoid the femoral bow, with a lower risk of fracture and under-sizing; Preserves bone stock for future revisions if required; Easier to remove if required

The femur begins to bow anteriorly at the 200 mm level, but may bow earlier in smaller people. If the stem to be used is less than 200 mm, a straight stem can be used. If the stem is longer than 200 mm, it will perforate the anterior femoral cortex. I know this because I did this on a few occasions more than 20 years ago. To use a long straight stem, there are two techniques. One can either do a diaphyseal osteotomy or one can do a Wagner split (extended trochanteric osteotomy). Both of these will put the knee in some degree of hyperextension, probably insignificant in the elderly, but it may be of significance in the young. In very young people, therefore, it may be preferable to use a bowed stem to avoid this degree of recurvatum. There are two different concepts of loading. Diaphyseal osteotomy implies a proximal loading has been sought. The Wagner split ignores the proximal femur and seeks conical fixation in the diaphysis. There will be very little bone-bone contact between what remains of the attached femur and the detached anterior cortex so that it is important to ensure that the blood supply to the anterior cortex remains intact, preferably by using Wagner's technique, using a quarter-inch osteotome inserted through the vastus to crack the medial cortex. Current modularity is of two types. Distal modularity was attempted many years ago and was never successful. Proximal modularity, as for example, the S-ROM stem, implies various sizes of sleeves fit onto the stem to get a proximal canal fill. In mid-stem modularity, the distal stem wedges into the cone. It has to be driven into where it jams and this can be somewhat unpredictable. For this reason, the solid Wagner stem has been replaced by the mid-stem modular. Once the distal femur is solidly embedded, the proximal body is then selected for height and version. The proximal body is unsupported in the mid-stem modular and initially, few fractures were noted at the taper junction. Cold rolling, shot peening and taper strengthening seem to have solved these problems. There are a variety of types of osteotomy, which can be used for different deformities. With a mid-stem modular system, generally, all that needs to be done is a Wagner-type split and fixation is sought in the mid-diaphysis by conical reaming. No matter what stem is used, distal stability is necessary. This is achieved by flutes, which engage the endosteal cortex. The flutes alone must have sufficient rotational stability to overcome the service loads on the hip of 22 Nm. I divide revision into three categories. In type one, the isthmus is intact, i.e. the bone below the lesser trochanter so that a primary stem can be used. In type two, the isthmus is damaged, i.e. the bone below the lesser trochanter, so a long revision stem is required. In a type three, there is more than 70 mm of missing proximal femur. The Wagner stem may be able to handle this on its own, but most other stems are better supported with a structural allograft cemented to the stem. The reported long term results of mid-stem modular revision implants are good as in most, over 90% survivorship. The introduction of modularity appears to have overcome initial disadvantage of the Wagner stem, i.e. its unpredictability in terms of leg length

The advent of Elastic Stable Intramedullary Nailing has revolutionised the conservative treatment of long human bone fractures in children (Metaizeau, 1988; Metaizeau et al., 2004). Unfortunately, failures still occur due to excessive bending and fatigue (Linhart et al., 1999; Lascombes et al., 2006), bone refracture or nail failure (Bråten et al., 1993; Weinberg et al., 2003). Ideally, during surgery, nail insertion into the diaphyseal medullary canal should not interrupt or injure cartilage growth; nails should provide an improved rigidity and fracture stabilisation. This study aims at comparing deflections and stiffnesses of nail-bone assemblies: standard cylindrically-shaped nails (MI) vs. new cylindrical nails (MII) with a flattened face across the entire length allowing more inertia and a curved tip allowing better penetration into the cancellous bone of the metaphysis (Figure 1). MII exhibits a section with two parameters: a diameter C providing nail stiffness and a height C' providing practical dimension when both nails are crossed at the isthmus of the diaphysis: C/C' is set to 1.25 for all MII nails. A CT scan of a patient aged 22 years was used to segment a 3D model of a 471mm-long right femur model. The medullary canal diameters at the isthmus are 10.8mm and 11.4mm in the ML and AP direction, respectively. Titanium-made CAD models of MI (Ø=4mm) and MII (flat face: Ø=5mm) were pre-curved to maintain their flat face and carefully placed and positioned according to surgeon's instructions. Both nails were inserted via lateral holes in the distal femur with their extremities either bumping against the cortex or lying in the trabecular bone. Transverse and comminuted fractures were simulated (Figure 1). For each assembly, a Finite Element (FE) tetrahedral mesh was generated (∼100181 nodes and 424398 elements). Grey-scale levels were used to assign heterogeneous material properties to the bone (E=6850 ρ. 1.49. (Morgan et al., 2003)). Two modes of loading were considered: 4-point bending (varus and recurvatum: F. max. =6000N) and internal torsion (M. max. =70kNmm). This led to the simulation of 15 FE models, including a reference intact femur. Results show that in valgus, for the transverse (comminuted) fracture, the mean displacement of the assembly decreased by around 50%: from 15.24mm (27.49mm) to 8.15mm (13.85mm) for MI and MII, respectively, compared to 3.59mm for the intact bone. The assembly stiffness increased by 87% and 99% for transverse and comminuted fracture, respectively (Table 1). Similar trends were found in recurvatum with higher increases in assembly stiffness of 170% and 143% for transverse and comminuted fracture, respectively (Table 1). In torsion, for the transverse (comminuted) fracture, the measured angle of rotation decreased from: 0.43rad (0.66rad) to 0.22rad (0.43rad) for MI and MII, respectively, compared to 0.09rad for the intact bone. This corresponded to an increase of 95% and 55% in assembly stiffness for transverse and comminuted fracture, respectively. In conclusion, using the 5mm-diameter new nails (MII) for the same intramedullar space, during either bending or torsion, assemblies were always stiffer than when using standard cylindrical nails

Background. Cement restrictors are used for maintaining good filling and pressurization of bone cement during hip and knee arthroplasties. The limitations of certain cement restrictors include the inability to accommodate for large medullary canals particularly in revision procedures. We describe a technique using SurgicelTM (Johnson & Johnson) and SPONGOSTAN™ (Johnson & Johnson) (Fig 1) to form a cement restrictor that can accommodate for large canal diameters and provide excellent pressurisation. Technique. The technique involves the application of SPONGOSTAN™ (Johnson & Johnson) foam onto a SurgicelTM (Johnson & Johnson) mesh which is then rolled onto the SPONGOSTAN™ foam forming a uniform cylindrical structure Figs 2,3. The diameter of the restrictor can be adjusted according to the desired femoral canal diameter through increasing the thickness of the SPONGOSTAN™ (Johnson & Johnson) foam. The restrictor is then inserted into the desired position in the medullary canal where it expands uniformly creating an effective restrictor and bone plug Fig 4. Bone cement is then applied and pressurisation commenced prior to the insertion of the implant Fig5. SPONGOSTAN™ is an absorbable haemostatic sponge intended for haemostatic use by applying to a bleeding surface. It consists of a sterile, water-insoluble, malleable, porcine gelatin absorbable sponge. Surgicel ™ is an absorbable hemostatic agent composed of oxidized regenerated cellulose. It is a sterile, absorbable knitted fabric that is flexible and adheres readily to bleeding surfaces. Both products are routinely used for their haemostatic properties in various surgical disciplines. Discussion. The use of intramedullary plugs in cemented total joint arthroplasty is essential in order to achieve good filling and pressurization in hip and knee arthoplasties, traditionally, a small piece of bone or a cement restrictor may be used to plug the shaft. Distal plugs seal the femoral canal, improve fixation and prevent bone cement from leaking during delivery and pressurization. Plugging the intramedullary canal during total hip arthroplasty increases penetration of cement into cancellous bone proximal to the intramedullary plug. Numerous plug designs and materials are available ranging from non-resorbable to resorbable. Regardless of design, all restrictors should avoid intramedullary cement leakage and plug migration during cement and stem insertion to ensure adequate intramedullary pressures. In some instances the diameter of the femoral canal is too wide to accommodate a conventional cement restrictor particularly when crossing the femoral isthmus and even more so in revision procedures requiring the implantation of long stemmed cemented components. The use of the Surgicel-Spongostan haemostatic restrictor overcomes some of the limitations of a standard cement restrictors. These include the ability to bypass a narrow femoral isthmus, accommodate large femoral canals, particularly in revision procedures, and the flexibility of adjusting the restrictor to the desired diameter of the medullary canal and in effect providing a bespoke cement restrictor. This technique was used successfully in over 300 revision hip and knee procedures with no adverse effects and excellent outcomes

INTRODUCTION: As the number of patients who have undergone total hip arthroplasty rises, the number of patients who require surgery for a failed total hip arthroplasty is also increasing. It is estimated that 183,000 total hip replacements were performed in the United States in the year 2000 and that 31,000 of these (17%) were revision procedures. Reconstruction of the failed femoral component in revision total hip arthroplasty can be challenging from both a technical perspective and in pre-operative planning. With multiple reconstructive options available, it is helpful to have a classification system which guides the surgeon in selecting the appropriate method of reconstruction. DISCUSSION: An extensively coated, diaphyseal filling component reliably achieves successful fixation in the majority of revision femurs. The surgical technique is straightforward and we continue to use this type of device in the majority of our revision total hip arthroplasties. However, in the severely damaged femur (Type IIIB and Type IV), other reconstructive options may provide improved results. Based on our results, the following reconstructive algorithm is recommended for femoral reconstruction in revision total hip arthroplasty: TYPE I: In a Type I femur, there is minimal loss of cancellous bone with an intact diaphysis. Cemented or cementless fixation can be utilised. If cemented fixation is selected, great care must be taken in removing the neo-cortex often encountered to allow for appropriate cement intrusion into the remaining cancellous bone. TYPE II: In a Type II femur, there is extensive loss of the metaphyseal cancellous bone and thus fixation with cement is unreliable. In this cohort of patients, successful fixation was achieved using a diaphyseal fitting, extensively porous coated implant in 26 of 29 cases (90%) However, as the metaphysis is supportive, a cementless implant that achieves primary fixation in the metaphysis can be utilized. TYPE III A: In a Type IIIA femur, the metaphysis is non-supportive and an extensively coated stem of adequate length is utilised to ensure that more than 4 cm of scratch fit is obtained in the diaphysis. TYPE III B: Based on the poor results obtained with a cylindrical, extensively porous coated implant, our present preference is a modular, cementless, tapered stem with flutes for obtaining rotational stability. Excellent results have been reported with this type of implant and by virtue of its tapered design, excellent initial axial stability can be obtained even in femurs with a very short isthmus. Subsidence has been reported as a potential problem with this type of implant and they can be difficult to insert. However, with the addition of modularity to many systems that employ this concept of fixation, improved stability can be obtained by impacting the femoral component as far distally as needed while then building up the proximal segment to restore appropriate leg length. TYPE IV: In a Type IV femur, the isthmus is completely non-supportive and the femoral canal is widened. Cementless fixation cannot be reliably used in our experience, as it is difficult to obtain adequate initial implant stability that is required for osseointegration. Reconstruction can be performed with impaction grafting if the cortical tube of the proximal femur is intact. However, this technique can be technically difficult to perform, time consuming and costly given the amount of bone graft that is often required. Although implant subsidence and peri-prosthetic fractures have been associated with this technique, it can provide an excellent solution for the difficult revision femur where cementless fixation cannot be utilised. Alternatively, an allograft-prosthesis composite can be utilised for younger patients in an attempt to reconstitute bone stock and a proximal femoral replacing endoprosthesis used for more elderly patients

Objective. The purpose of this study was to compare the proximal femoral morphology between normal Chinese and Caucasian populations by 3D analysis derived from CT data. Materials and Methods. 141 anonymous Chinese femoral CT scans (71 male and 70 female) with mean age of 60.1years (range 20–93) and 508 anonymous Caucasian left femoral CT scans (with mean age of 64.8years (range 20–93). The CT scans were segmented and converted to virtual bones using custom CT analytical software. (SOMA™ V.4.0) Femoral Head Offset (FHO) and Femoral Head Position (FHP) were measured from head center to proximal canal central axis and to calcar or 20mm above Lesser Trochanter (LT) respectively. The Femoral neck Anteversion (FA) and Caput-Collum-Diaphyseal (CCD) angles were also measured. The Medial Lateral Widths(MLW. n. ) of femoral canal were measured at 0, -10, LT, -30, -40, -60, -70 and -100mm levels from calcar. Anterior Posterior Widths (APW. n. ) were measured at 0, -60 and -100mm levels. The Flare Index (FI) was derived from the ratio of widths at 0 and -60mmor FI=W. 0. /W. −60. All measurements were performed in the same settings for both populations. The comparison was analyzed by Student T test. P<0.05 was considered significant. Results. The average FHO and FHP of Chinese were 38.4mm and 25.2mm and were both shorter than 42.1mm and 29.7mm of Caucasian's, P=2.3E-15 and P=1.7E-10. (Figure 1) CCD angle was 130.3° comparing to 127.7° of Caucasian P=1.5E-05. Chinese FA angle was 15.6° and Caucasian's was 14.7°, P=0.31. The average MLW. 1-8. were 43.1, 34.6, 28.5, 23.8, 20.6, 17, 16.2 and 14.4mm for Chinese and 43.7, 35.0, 28.7, 24.0, 20.6, 16.7, 15.7 and 13.5mm for Caucasian. P=9.4E-02, .32, .47, .50, .93, .20, .02 and 1.7E-05 respectively. (Figure 2) The average APW. 1-3. were 35.9, 15.5 and 13.7mm for Chinese and 43.7, 15.2 and 12.5mm for Caucasian. P=4E-62, 0.11 and 7.4E-10. (Figure 3) The total medial/lateral and medial/center FI were 2.5 and 2.8 for Chinese, 2.6 and 2.9 for Caucasian. P=.004 and 4.5E-06. The total anterior/posterior and anterior/center FI were 2.3 and 2.6 for Chinese, 2.9 and 2.5 for Caucasian. P=5.3E-61 and 8.5E-04. Conclusion and Discussion. Chinese had significantly lower FHO, FHP, APW. calcar. , FI. medial, M-L. and FI. A-P. ; significantly higher CCD angle and MLW. isthmus. , APW. isthmus. and FI. anterior. than that of Caucasian population. There were no significant differences in FA and MLW from 10mm above to 50mm bellow LT. The average reduction of 3.7mm in FHO and 4.5mm in FHP for Chinese suggests a necessary adjustment of femoral implant neck length designed for Caucasian population. Due to the findings of the similarity in MLW and dissimilarity in APW, the study suggested the M-L fitting stem will fit well for both populations

Femoral components in total hip replacements fail in well-known ways. There is vertical sink, posterior rotation and pivot, either distal or mid-stem. In order to sink, the stem moves into valgus and then slides down the inside of the calcar. It does not cut through the calcar. To prevent sink and pivot, a canal filling stem is required. Canal fill prevents the stem from moving into valgus and, therefore, it will not sink. Two centimeters with complete canal fill is adequate in a primary stem. A long stem will give longer canal fill in a revision. Sharp distal flutes will prevent rotation. The distal end of the stem should be polished. One is looking for a distal stability, not distal fixation. If the isthmus is intact, a primary stem can be used. If the isthmus is damaged, a long stem is necessary. If the calcar is intact, a primary neck is adequate. If the calcar is missing down to the level of the lesser trochanter, a calcar replacement neck is required. If there is more than 70 millimeters of completely missing proximal femur, a structural allograft is required. If the proximal femur is damaged, the ability to place a sleeve or collar to seek the best bone available independently of the stem version is very helpful. No matter how poor the proximal bone quality is, it can be supplemented by cerclage wires. The implant will sink only if the cerclage wires break. The advantage of proximal fixation is that loading the proximal femur speeds recovery. The huge disadvantage of distal fixation is removal of the implant should it become necessary. My long term results for the S-ROM stem used in revision are now out over 20 years. There were 119 primary stems with a minimum follow up of 5 years with no revisions for aseptic loosening. There were 262 long stems used. Nine (3.7%) underwent aseptic loosening. Most of these were due to technical errors due to my inexperience in the learning process of revision surgery. Four were dependent on strut-grafts and should have been treated with structural allografts. There were seven cases with structural allografts. Three were revised. Again, these were largely from problems arising from inexperience. I believe proximal modularity with distal stability allows the vast majority of revision cases to be treated with proximal fixation

Introduction:. Extensive bone defects of the proximal femur e.g. due to aseptic loosening might require the implantation of megaprostheses. In the literature high loosening rates of such megaprostheses have been reported. However, different fixation methods have been developed to achieve adequate implant stability, which is reflected by differing design characteristics of the commonly used implants. Yet, a biomechanical comparison of these designs has not been reported. The aim of our study was to analyse potential differences in the biomechanical behaviour of three megaprostheses with different designs by measuring the primary rotational stability in vitro. Methods:. Four different stem designs [Group A: Megasystem-C® (Link), Group B: MUTARS®(Implantcast), Group C: GMRS™ (Stryker) and Group D: Segmental System (Zimmer); see Fig. 1] were implanted into 16 Sawbones® after generating a segmental AAOS Typ 2 defect. Using an established method to analyse the rotational stability, a cyclic axial torque of ± 7.0 Nm along the longitudinal stem axis was applied. Micromotions were measured at defined levels of the bone and the implant [Fig. 2]. The calculation of relative micromotions at the bone-implant interface allowed classifying the rotational implant stability. Results:. All four different implants exhibited low micromotions, indicating adequate primary stability. Lowest micromotions for all designs were located near the femoral isthmus [Fig. 3]. The extent of primary stability and the global implant fixation pattern differed considerably and could be related to the different design concepts. Discussion:. Compared to other implant designs, all stems resulted in low relative motions regardless their design. The conical Megasystem-C® stem seems to lock in the proximal isthmus of the femur, whereas the MUTARS® stem seems to have a total fixation. Its hexagonal cross-section might have a good interlocking effect against rotational force application. Similarly, the GMRS™ stem shows a total fixation with little tendency to the distal part. The very rough porous-coated surface seems to generate a comparable fixation method to the hexagonal MUTARS® stem. However, the four longitudinal expansions in the proximal part of the GMRS™ stem might not have such a high rotational stability effect as expected. Compared to the other stems, the Segmental System stem showed very low relative micromotions in the proximal part. This sharp fluted stem seems to engrave itself into the bone. Within this study all stems seemed to achieve an adequate primary rotational stability. We could show that stem design could qualitatively and quantitatively influence the initial fixation behavior of megaprostheses regarding biomechanical tests, like primary stability measurements in synthetic femurs. These experiences should be considered regarding the choice of stem fixation design in specific defect situations

As the number of patients who have undergone total hip arthroplasty rises, the number of patients who require surgery for a failed total hip arthroplasty is also increasing. It is estimated that 183,000 total hip replacements were performed in the United States in the year 2000 and that 31,000 of these (17%) were revision procedures. Reconstruction of the failed femoral component in revision total hip arthroplasty can be challenging from both a technical perspective and in preoperative planning. With multiple reconstructive options available, it is helpful to have a classification system which guides the surgeon in selecting the appropriate method of reconstruction. A classification of femoral deficiency has been developed and an algorithmic approach to femoral reconstruction is presented. An extensively coated, diaphyseal filling component reliably achieves successful fixation in the majority of revision femurs. The surgical technique is straightforward and we continue to use this type of device in the majority of our revision total hip arthroplasties. However, in the severely damaged femur (Type IIIB and Type IV), other reconstructive options may provide improved results. Based on our results, the following reconstructive algorithm is recommended for femoral reconstruction in revision total hip arthroplasty. Type I: In a Type I femur, there is minimal loss of cancellous bone with an intact diaphysis. Cemented or cementless fixation can be utilised. If cemented fixation is selected, great care must be taken in removing the neo-cortex often encountered to allow for appropriate cement intrusion into the remaining cancellous bone. Type II: In a Type II femur, there is extensive loss of the metaphyseal cancellous bone and thus, fixation with cement is unreliable. In this cohort of patients, successful fixation was achieved using a diaphyseal fitting, extensively porous coated implant. However, as the metaphysis is supportive, a cementless implant that achieves primary fixation in the metaphysis can be utilised. Type IIIA: In a Type IIIA femur, the metaphysis is non-supportive and an extensively coated stem of adequate length is utilised to ensure that more than 4cm of scratch fit is obtained in the diaphysis. Type IIIB: Based on the poor results obtained with a cylindrical, extensively porous coated implant (with 4 of 8 reconstructions failing), our present preference is a modular, cementless, tapered stem with flutes for obtaining rotational stability. Type IV: The isthmus is completely non-supportive and the femoral canal is widened. Cementless fixation cannot be reliably used in our experience, as it is difficult to obtain adequate initial implant stability that is required for osseointegration. Reconstruction can be performed with impaction grafting if the cortical tube of the proximal femur is intact. However, this technique can be technically difficult to perform, time consuming and costly given the amount of bone graft that is often required. Although implant subsidence and peri-prosthetic fractures have been associated with this technique, it can provide an excellent solution for the difficult revision femur where cementless fixation cannot be utilised. Alternatively, an allograft-prosthesis composite can be utilised for younger patients in an attempt to reconstitute bone stock and a proximal femoral replacing endoprosthesis used for more elderly patients

Robotic surgical systems reduce the cognitive workload of the surgeon by assisting in guidance and operational tasks. As a result, higher precision and a decreased surgery time are achieved, while human errors are minimised. However, most of robotic systems are expensive, bulky and limited to specific applications. In this paper a novel semi-automatic robotic system is evaluated, that offers the high accuracies of robotic surgery while remaining small, universally applicable and easy to use. The system is composed of a universally applicable handheld device, called Smart Screwdriver (SSD) and an application specific kinematic chain serving as a tool guide. The guide mechanism is equipped with motion screws. By inserting the SSD into a screw head, the screw is identified automatically and the required number of revolutions is executed to achieve the desired pose of the tool guide. The usability of the system was evaluated according to IEC 60601-1-6 using pedicle screw implementation as an example. The achieved positioning accuracies of the drill sleeve were comparable to those of fully automatic robotic systems with −0.54 ± 0.93 mm (max: − 2.08 mm) in medial/lateral-direction and 0.17 ± 0.51 mm (max: 1.39 mm) in cranial/caudal- direction in the pedicle isthmus. Additionally, the system is cost-effective, safe, easy to integrate in the surgical workflow and universally applicable to applications in which a static position in one or more DOF is to be adjusted

Implant, surgeon, and patient-related factors all contribute to the risk of revision requiring an ETO. It is shown in the literature that the ETO can be a successful and easy-to-be-performed technique, but it can also lead to a bunch of complications, like peri-prosthetic fracture, loosening of the implant, damage of the isthmus and especially nonunion of the greater trochanter, which could result in an insufficiency limping with positive Trendelenburg Sign. We do not believe in the necessity of an extended trochanteric osteotomy, which is extremely rarely performed at our institution. In almost all cases, the stem can be removed using an endofemoral approach from the top. Special instruments are necessary, and retrograde slap hammers are helpful. In general, cortical windows may be required to gain access to the bone-implant interface, but only in cases of well-fixed cementless components or if the distal cement is difficult to reach and remove. A full range of narrow and wide osteotomes of various thicknesses should be available. Those are our most important tools. Multiple osteotomes, which are carefully driven between the interfaces from all sides, can be gradually wedged or forced out of their cement mantle, even if stemmed. Generally, cemented and cementless procedures could be considered for reconstruction. We recommend performing the procedure only when the surgeon is proficient. This papers tries to provide such strategies

As the number of patients who have undergone total hip arthroplasty rises, the number of patients who require surgery for a failed total hip arthroplasty is also increasing. Reconstruction of the failed femoral component in revision total hip arthroplasty can be challenging from both a technical perspective and in preoperative planning. With multiple reconstructive options available, it is helpful to have a classification system which guides the surgeon in selecting the appropriate method of reconstruction. We have developed a classification of femoral deficiency and an algorithmic approach to femoral reconstruction is presented. Type I: Minimal loss of metaphyseal cancellous bone with an intact diaphysis. Often seen when conversion of a cementless femoral component without biological ingrowth surface requires revision. Type II: Extensive loss of metaphyseal cancellous bone with an intact diaphysis. Often encountered after the removal of a cemented femoral component. Type IIIA: The metaphysis is severely damaged and non-supportive with more than four centimeters of intact diaphyseal bone for distal fixation. This type of defect is commonly seen after removal of grossly loose femoral components inserted with first generation cementing techniques. Type IIIB: The metaphysis is severely damaged and non-supportive with less than four centimeters of diaphyseal bone available for distal fixation. This type of defect is often seen following failure of a cemented femoral component that was inserted with a cement restrictor and cementless femoral components associated with significant distal osteolysis. Type IV: Extensive meta-diaphyseal damage in conjunction with a widened femoral canal. The isthmus is non-supportive

Revision of the failed femoral component of a total hip arthroplasty can be challenging. Multiple reconstructive options are available and the operation itself can be particularly difficult and thus meticulous pre-operative planning is required to pick the right “tool” for the case at hand. The Paprosky Femoral Classification is useful as it helps the surgeon determine what bone stock is available for fixation and hence, which type of femoral reconstruction is most appropriate. Monoblock, fully porous coated diaphyseal engaging femoral components are the “work-horse” of femoral revision and are used in my practice for approximately 70% of reconstructions. These stems are associated with problems, in the following situations: The canal diameter is greater than 18mm; There is less than 4cm available for distal fixation in the isthmus; There is proximal femoral remodeling into retroversion. When the limits of monoblock stems are exceeded, we use modular tapered femoral components. These stems in general allow for better fixation in short isthmic segments and the bi-body nature allows for independent positioning of the proximal body, which is particularly helpful when the femur has remodeled into retroversion

The aim of this paper is to describe the technique and evaluate the effectiveness of the RIA system in the first cases of bone loss treated by the authors with this technique. Between January 2010 and January 2011, ten patients were treated with an average age of fourty six years, with infected bone loss as a result of open fractures in various bone segments, with multiple failed treatment attempts, including three humeri, four femurs and three tibiae. The average size of the initial bone loss was 4 cm, varying from 1 to 8 cm. In 4 patients it was used simultaneously a Ilizarov apparatus with acute compression of the focus, in two patients a Ender pin and monolateral external fixator, three other cases with a SAFE nail with core with antibiotics and in one case an osteosynthesis with a plate and screws. The RIA was introduced with a percutaneous technique with a one pass drilling. The graft thus collected was mixed with appropriate antibiotics and aplied at the defect. The volume of the harvested graft, complications of the donor and recipient and the final results was recorded. The review showed that the average volume of graft was 60 cc, from 20 to 90 cc. In two female patients older than 70 years with osteoporosis, insufficient bone of poor quality was obtained. Problems included a case of iatrogenic fracture of the donor site, due to poor surgical technique and a case of relapse of the nonunion. Regarding the effectiveness of grafts extracted with the RIA system, 90% of the cases achieved consolidation in average of 5 months after grafting, range 3–9 months. This short experience with the RIA system showed that it is an attractive method allowing a rapid removal of a large volume of bone graft with a minimally invasive approach and a short learning curve. It is not indicated in elderly patients with osteoporosis and those with a narrow medullar canal less than 11 mm. Special attention must be done to the need to choose a drill no larger than 1 mm of the diameter of the isthmus, to do a single entry point and with only one drill passage to prevent the weakening of the donor site

As the number of patients who have undergone total hip arthroplasty rises, the number of patients who require surgery for a failed total hip arthroplasty is also increasing. Reconstruction of the failed femoral component in revision total hip arthroplasty can be challenging from both a technical perspective and in pre-operative planning. With multiple reconstructive options available, it is helpful to have a classification system which guides the surgeon in selecting the appropriate method of reconstruction. Type I: Minimal loss of metaphyseal cancellous bone with an intact diaphysis. Often seen when conversion of a cementless femoral component without biological ingrowth surface requires revision. Type II: Extensive loss of metaphyseal cancellous bone with an intact diaphysis. Often encountered after the removal of a cemented femoral component. Type IIIA: The metaphysis is severely damaged and non-supportive with more than 4 cm of intact diaphyseal bone for distal fixation. This type of defect is commonly seen after removal of grossly loose femoral components inserted with first generation cementing techniques. Type IIIB: The metaphysis is severely damaged and non-supportive with less than 4 cm of diaphyseal bone available for distal fixation. This type of defect is often seen following failure of a cemented femoral component that was inserted with a cement restrictor and cementless femoral components associated with significant distal osteolysis. Type IV: Extensive meta-diaphyseal damage in conjunction with a widened femoral canal. The isthmus is non-supportive. Based on our results, the following reconstructive algorithm is recommended for femoral reconstruction in revision total hip arthroplasty. An extensively coated, diaphyseal filling component reliably achieves successful fixation in the majority of revision femurs and the surgical technique is straightforward. However, in the severely damaged femur (Type IIIB and Type IV), other reconstructive options may provide improved results. Type I: Cemented or cementless fixation can be utilised. If cemented fixation is selected, great care must be taken in removing the neo-cortex often encountered to allow for appropriate cement intrusion into the remaining cancellous bone. Type II: In this cohort of patients, successful fixation was achieved using a diaphyseal fitting, extensively porous coated implant. However, as the metaphysis is supportive, a cementless implant that achieves primary fixation in the metaphysis can be utilised. Type IIIA: An extensively coated stem of adequate length is utilised to ensure that more than 4 cm of scratch fit is obtained in the diaphysis. Type IIIB: Our present preference is a modular, cementless, tapered stem with flutes for obtaining rotational stability. Type IV: Cementless fixation cannot be reliably used in our experience, as it is difficult to obtain adequate initial implant stability that is required for osseointegration. Reconstruction can be performed with impaction grafting if the cortical tube of the proximal femur is intact. However, this technique can be technically difficult to perform, time consuming and costly given the amount of bone graft that is often required. Although implant subsidence and peri-prosthetic fractures (both intra-operatively and post-operatively) have been associated with this technique, it can provide an excellent solution for the difficult revision femur where cementless fixation cannot be utilised. Alternatively, an allograft-prosthesis composite can be utilised for younger patients in an attempt to reconstitute bone stock and a proximal femoral replacing endoprosthesis used for more elderly patients