Aims. There are concerns regarding initial stability and early periprosthetic fractures in cementless hip arthroplasty using short stems. This study aimed to investigate stress on the cortical bone around the stem and micromotions between the stem and cortical bone according to femoral stem length and positioning. Methods. In total, 12 femoral finite element models (FEMs) were constructed and tested in walking and stair-climbing. Femoral stems of three different lengths and two different positions were simulated, assuming press-fit fixation within each FEM. Stress on the cortical bone and micromotions between the stem and bone were measured in each condition. Results. Stress concentration was observed on the medial and lateral interfaces between the cortical bone and stem. With neutral stem insertion, mean stress over a region of interest was greater at the medial than lateral interface regardless of stem length, which increased as the stem shortened. Mean stress increased in the varus-inserted stems compared to the stems inserted neutrally, especially at the lateral interface in contact with the stem tip. The maximum stress was observed at the lateral interface in a varus-inserted short stem. All mean stresses were greater in stair-climbing condition than walking. Each micromotion was also greater in shorter stems and varus-inserted stems, and in stair-climbing condition. Conclusion. The stem should be inserted neutrally and stair-climbing movement should be avoided in the early postoperative period, in order to preserve early stability and reduce the possibility of thigh pain, especially when using a shorter stem. Cite this article: Bone Joint Res 2021;10(4):250–258

Introduction. Failed operated intertrochanteric fractures (with screw cutout, joint penetration, varus collapse, nonunion, or femoral head avascular necrosis) pose treatment dilemmas. The ideal approach is re-osteosynthesis with autologous bone grafting. When the femoral head is unsalvageable, conversion to a prosthetic hip replacement is necessary. Materials/Methods. Thirty-seven patients with failed dynamic hip screw fixation (and unsalvageable femoral heads) were treated with cementless hip arthroplasty (13 underwent Bipolar Arthroplasty, 24 had Total Hip Arthroplasty) over a 5-year period (Dec 2005 to Nov 2010). Seven needed a modified trochanteric split, and the rest were managed by standard anterolateral approach. Abductor mechanism was reconstructed using strong nonabsorbable sutures (ethibond 5) or stainless steel wires. The calcar was partially reconstructed using remnant femoral head and cerclage wiring in a few cases. Results. Clinico-radiological assessment was done at three, six, 12 months and yearly thereafter over an average 36 months (range, three to 60 months). Stem loosening, lysis, subsidence and trochanteric union were studied. At last follow-up, one patient had died, and there were two instances each of stem subsidence and trochanteric nonunion. Clinical results using Harris hip scores were good or excellent. Conclusion. Management of nonsalvageable femoral heads after failed intertrochanteric fracture fixation is possible with cementless hip arthroplasty. Successful outcomes depend on functional abductor reconstruction, fracture and femoral shaft penetration prevention. Autograft, allograft or head/neck replacement components are necessary sometimes

We studied the pattern of . 99m. Tc-methylene diphosphonate uptake around uncemented femoral components in 44 asymptomatic hip arthroplasties, performing isotope scans at intervals from 4 to 48 months after operation. We used phase-III images obtained with a high-resolution gamma camera and measured the activity in various zones using a specially designed computer program. The components studied at 4, 6, 9 and 12 months were coated with hydroxyapatite (HA) and those studied at 18, 24, 36 and 48 months were not coated. We found a statistically significant fall in activity between four and six months around HA-coated prostheses in all five femoral periprosthetic zones. After six months activity was relatively uniform, but remained higher than that in normal femoral bone at 48 months in non-coated prostheses. We discuss the application of these patterns in the evaluation of painful cementless hip arthroplasties

We have analysed the clinical results of a cementless hip replacement using a Moore stem with a smooth surface, and correlated these results with the radiological changes. Forty-two consecutive arthroplasties in 41 patients were studied prospectively and reviewed at a minimum of two and up to six years; 63% had a good clinical result, 18.5% a fair result, and 18.5% a poor result. Thigh pain on weight-bearing was the main problem and was due to loosening of the stem. We caution against the use of this implant in arthritic patients, in whom a good result can be obtained more predictably with cement fixation

We present the case of a 65-year-old man who developed a malignant fibrous histiocytoma at the lesser trochanter five months after a cementless hip replacement. We have reviewed reports of similar cases and discuss them in terms of the possible mechanisms of sarcomatous degeneration and the latency of such changes

Introduction. Iatrogenic proximal femur hoop-stress fracture is a recognised complication of uncemented hip arthroplasty. It has a reported incidence of two to three percent and increases patient morbidity. We describe a novel technology that predicts fracture in real-time by less than one minute. Method. Four proximal femora from red deer (Cervus elaphus), similar size to human proximal femora, were prepared to accept an uncemented hip arthroplasty femoral rasp (Finsbury Orthopaedics) and then mounted in a loading machine. The femora were fresh-frozen, defrosted and kept at room temperature in 0.9% saline swabs. The rasp was forced into each femur in repeated loading cycles every 10 seconds, in steps of 100N increasing from 200N to over 2000N until fracture, in a manner to simulate surgery. One sensor was attached to the surface of the proximal femur and one to the femoral rasp. The sensor outputs were recorded, analysed and displayed on a PC using a software algorithm to show signal energy (joules) and amplitude (decibels). The proximal femur was coated with specular marking paint to permit real-time 3-D digital image correlation (DIC) analysis. DIC is an established tool in engineering fracture analysis and utilises two spatially orientated video cameras to measure surface strain and fracture. The femur was observed by the human eye and loaded in cycles until a fracture was seen. The moment of fracture was marked in the recording timeline. DIC was used to confirm fracture. Results. All femora fractured in the anterior proximal cortex. Signals from both sensors were identical in form and differed by less than five percent in strength during loading. Both signals demonstrated significant increases in energy and amplitude shortly prior to fracture. Early during loading cycles the femoral rasp subsided and became well-fixed within the femur; this was associated with signals of 60-70dB. During later loading cycles the rasp ceased to subside in the femur and was well-fixed in a press-fit; subsequent loading caused fracture and this was preceded by a greater number of stronger signals of over 90dB. The increase occurred 1 to 3 loading cycles prior to fracture, or less than 30 seconds. DIC was used to confirm the presence of a fracture visible to the human eye. At the time of the first significant increase in signal there was no crack visible to the eye or to DIC analysis and the femoral rasp did not subside further into the femur. Conclusions. During press-fitting of an uncemented femoral rasp in a deer femur a significant change in signal characteristics occurs shortly prior to a fracture being visible to the eye and detectable by DIC analysis. The almost identical signal output from both sensors suggests that one single sensor mounted on a femoral rasp will suffice, thereby removing the need to expose more of the proximal femur during surgery. This technology may be able to predict and therefore prevent femur fracture during uncemented hip arthroplasty. Further research is necessary in animal and human cadavers to explore and validate this research

Background:. Historically, performing a successful hip joint replacement in patients aged fewer than 30 years has been an orthopedic challenge. The newer generation of prostheses and surgical techniques has the potential to increase the longevity of implants. The purpose of this study was to evaluate the outcomes of cementless hip arthroplasty in patients aged fewer than 30 years. Materials and Methods:. In this cross-sectional study, 41 patients (46 hips) were studied with a mean age of 24, 4 (from 17 to 30 years) of whom underwent cementless metal – polyethylene hip arthroplasty from 2004 to 2007. The Harris hip score (HHS) was used to assess the functional consequences. Patients were followed up in terms of early complications (thrombophlebitis of the lower limbs, dislocation, hematoma and infection) and late complications (aseptic loosening, dislocation, and reoperation) at weeks 3 and 6, at 3 and 6 months, one year after surgery and annually thereafter. Results:. Patients were followed for an average of 5 years and 2 months (from 51 to 82 months). One early complication (symptomatic thrombophlebitis) and one late dislocation (2.2%) were observed. There were no cases of aseptic loosening or osteolysis at the end of follow-up. The preoperative HHS was 59.6 (from 41 to 76), which rose to 82 and 83.5 after the one-year and final follow-up, respectively, which was a significantly increase. Conclusions:. Hip arthroplasty using a new generation of cementless proximal porous prosthesis with resistant polyethylene to cover the joint surfaces in patients aged fewer than 30 years is satisfactory and is accompanied by low complications. Keywords: Total hip replacement, hip arthroplasty, cementless Prosthesis, Hip osteoarthritis, osteonecrosis

Introduction: It is not uncommon situation, in a hip fracture patient treated with dynamic hip screw(DHS) system, that the hip arthroplasty should be done after removal of DHS. However multiple screw holes and postplating osteopenia under the barrel plate will be created in the proximal femur resulting adverse mechanical effects. Purpose: The authors analysed the micromotion of femoral stem and the stress concentration of proximal femur in hip replacement performed after removal of DHS using finite element analysis. Methods: For simulation of femoral cortical defects after removal of 4-holed DHS system, four Φ4.5 mm cortical screw holes on medial and lateral cortices of the femur and one Φ12mm lag screw. One 20mmx90mm weakened cortical bone area on lateral cortex was made for simulation of the postplating osteopenia created under the barrel plate. After meshing with eight node linear hexahedron, nonlinear contact analysis was done using ABAQUS 5.8 package system. For the postplating osteopenia we decreased the bony strength of cortical bone up to 20%. Results: In one leg stance, the maximal micromotions at metal to bone interface were around 150& #13211; (142.3-160.6& #13211;) even in the osteoporotic femur. However, in stair climbing, it increased over 150& #13211; (170.1-191.1& #13211;) even in the non-osteoporotic intact femur. The maximal micromotions were 170.1& #13211; in intact non-osteoporotic femur and 191.1& #13211; in osteoporotic DHS removed femur in a stair climbing. The pattern of stress distribution on the surface of the femur was changed showing distal transfer of the point with maximal stress from the proximal medial area to the stem tip area. The maximal stress increased up to 89% at the lag screw hole. Conclusion: This study suggests that the femoral stem for primary cementless hip replacement could be used in the DHS removed femur regardless of bone quality, if it is long enough to pass the screw holes and also if the post-operative rehabilitation is strictly controlled

Introduction

Undersizing of an uncemented femoral stem is a post-operative description of a radiograph with unclear clinical importance. It may not always translate into a suboptimal clinical outcome.

Aims

Cementless femoral stems must be correctly sized and well-seated to obtain satisfactory biological fixation. The change in sound that occurs during impaction of the femoral broach is said to indicate good fit, but this has not been widely studied. We set out to find whether the presence or absence of these sound changes could predict correct sizing.

Introduction: Hip arthroplasty for dysplasia of the hip provides a challenge to all hip surgeons. The choice of prosthesis used depends on the severity of the deformity, and the challenge of acetabular reconstruction. We report a review of 105 of our cases operated since 1992 with a minimum two-year follow-up.

Methods: The data in this study has been collected and entered prospectively since 1992 on an arthroplasty database. A total of 105 cases were identified and reviewed. The indication for surgery was painful hip osteoarthritis secondary to dysplasia. All patients were reconstructed with some attempt at restoration of the hip centre, and without femoral osteotomy.

Results: There were 96 patients (10 bilateral), 66 females and 29 males whose mean age at surgery was 53 years (23 to 97 years). The mean follow-up period was 59 months (27 to 107 months). The hip was exposed via a posterior approach in 98% of cases. The majority (94%) of cases had no previous surgery. Depending on the degree of dysplasia either an ABG or S-ROM prosthesis was used.

There were 78 Crowe I & II, and 18 Crowe III & IV hips. The more dysplastic hips required the versatility of the SROM stems to avoid excessive lengthening or femoral osteotomy. These cases also had significantly more inferior reconstruction of the hip centre, and medialisation of the hip centre.

Complications occurred in 8/106 (8%) of cases, the mean time to occurrence being 25 months. The majority were dislocations 7 (7%). There were no sciatic nerve palsies. Revision was required for 5 cups and 1 stem. Clinical evaluation showed all patients were living at home and 85% had no activity restrictions. Mean Harris Hip Score was 92/100. None or mild thigh pain only was reported in 90% of cases. In 98% of cases patients were satisfied with their outcome. Radiographic evaluation showed stem ingrowth occurred in all cases. Minor osteolysis was apparent in 6% of cases. Spot welds were identified in 76% of cases. One case demonstrated pedestal formation.

Conclusion: Reconstructing hip joint mechanics is a challenge in the dysplastic hip. The use of different prostheses for the varying severity in dysplasia has been an effective approach to optimise hip mechanics. Our results using this approach with cementless implants has given excellent short term clinical and radiographic results.

We examined a group of 26 patients (28 hip joints) with postdysplastic osteoarthritis who were operated in 1995 and 1996.

The Zweymüller Bicon prosthesis was used in all cases. Only patients with dysplasia Type B and C according to Eftekhar were included. By the method of Ranawat and Pagnana, the true acetabular region and the approximate femoral head centre were determined on preoperative and postoperative radiographs. The patients were controlled in 1999 with HHS. Antero-posterior radiographs of the pelvis and lateral radiographs of the acetabulum according to Zweymüller were made in all hips.

In most of the operated hip joints the true center of the rotation differed from the ideal centre, with the maximal difference being 18 mm cranially. Cranial placement of the cup occurred more frequently in Type C. No patient was reoperated, and as determined by radiographs, there were no indications of loosening in the acetabular and femoral components.

The Zweymüller Bicon total hip joint endoprosthesis is suitable in most cases of postdysplastic osteoarhritis of the hip. No special or individual implant was necessary in 1995 and 1996. Good primary stability and a good result was achieved in all cases. We consider this type of hip implant as especially useful in CDH osteoarthritis.

Introduction: Developmental dysplasia of the hip (DDH) is a common cause of secondary osteoarthritis of the hip. The severity of the hip dysplasia varies considerably leading to a broad spectrum of reconstructive challenges. The custom CAD/CAM femoral stems offer a useful solution to fit and correct the abnormalities in the anatomy of the proximal femur.

Materials and Methods: The purpose of the study was to review at the functional and radiological outcome of uncemented CAD/CAM stems where the primary diagnosis is DDH. Uncemented sockets were used in all cases. Pre-operative planning consisted of a CT scan to assess the available acetabular coverage, estimate the degree of femoral anteversion and precisely evaluate the limb-length inequality. The hips were classified according to Crowe and Hartofilakidis. Patients with less than two-year follow up were excluded. The outcome was determined radiologically and using the Harris, Oxford and WOMAC scoring systems.

Results: Ninety-nine cases were identified and included in the study. The mean age of the group was 43.8 (range 26–79) with a female to male ratio was 4 to 1. The average follow up time was 5 years (range 24–118). The majority of the patients had excellent outcomes with a significant improvement in their clinical scores. The pre-operative scores were Harris Hip score 43.8 (range 9–81), Oxford 41.6 (range 19–59) and WOMAC 77.3 (range 10–120). Post operatively the scores have improved to Harris Hip Score 84.2 (range 38–99), Oxford 20.3 (range 12–48) and WOMAC 37.1 (range 24–92).

Conclusion: Total hip replacement for the sequelae of hip dysplasia is associated with high failure and complication rates. CAD/CAM stems afford a great deal of flexibility for the management of a broad spectrum of anatomical problems in these cases and provide a very useful alternative to modular prostheses. We present excellent medium term results.

Since 1964, 3573 uncemented Ring total hip replacements of all types have been performed; 194 (5.4%) have required revision for infection, loosening or breakage. Of these, 102 were available for review; 81 had satisfactory results five years after operation. These results are better than many of those reported after revision of cemented hip replacements. It is suggested that the absence of cement makes revision easier because bone erosion rarely occurs.

Introduction

Conversion of immovable hip to a total hip arthroplasty provides a solution, improving function, reducing back and knee pain, and slowing degeneration of neighboring joints associated with hip dysfunction while the mobilization by total hip arthroplasty is rather uncommon and challenging surgery.

Introduction and Objectives: One of the complications of hip arthroplasty is intraoperative fractures of the femur. In this study, we reviewed the incidence of intraoperative fractures in 118 hip arthroplasty surgeries using a stem from Meridian Howmedica, Rutherford, New Jersey, in an attempt to analyse the risk factors for intra-operative fractures and their relationship to short-term radiographic characteristics of the prosthesis. Our aim is to determine if there are risk factors associated with a higher incidence of intraoperative fractures in the following categories: patient, shape and dimensions of the femur, and relative size of the implant with respect to the medullary cavity. We will also determine if short-term follow up of patients with fractures yields radiographic information to indicate early loosening of the prosthesis.

Materials and Methods: We studied 118 implants from consecutive operations performed from January 1997 to December 2000. The following variables were evaluated: general patient factors; local factors (characteristics of the femur); previous treatments, degree of femoral osteoporosis, type of femur, cervicodiaphyseal angle, femoral flring, “canal flare index”, cortical index, canal width 20mm proximal to the lesser trochanter, at the lesser trochanter, and 20mm distal to the lesser trochanter, pre-operative proximal and distal measurement of the stem, and if this coincides with the actual size of the stem; intraoperative factors: type of anaesthesia, patient positioning, surgical approach, experience of the surgeon, surgical time, the need for transfusion and number of units, the use of prophylactic cerclage, detection and localization of the intraoperative femoral fracture, and treatment of the same when they occurred; postoperative radiographic factors: level of cutting femoral neck, orientation of the stem (varus or valgus), proximal and distal stem size, proximal and distal packing of the canal, and length of the neck of the head of the prosthesis; radiographic factors 12 months postoperatively: stem orientation (varus or valgus), rounding of the calcar, cortical thickening, osteolysis, osteopenia, the presence of a ledge, the presence of lines of sclerosis, sinking of the stem, loosening of the ball, and the type of integration of the stem into the bone.

Results: Of the 118 cases that were studied, intraoperative fractures occurred in 13 cases, representing an incidence of 11.01%, a somewhat higher rate than others have reported. We analyzed the occurrence of fractures in relation to the different variables in our study. We found a higher incidence of fractures in type A femurs (p< 0.05) and in cases of greater proximal filling by the implant (p< 0.05).

Discussion and Conclusions: Though our study is limited in number of patients and length of follow-up time, it has demonstrated that the incidence of intraoperative fractures is associated with a narrow metaphyseal medullary cavity and predominately with a type A femur, which is a femur with low “canal flare index” values. Furthermore, since the risk of fracture is greater when we attempt to significantly adjust the size of the pros-thesis to the metaphysis, the incidence of fractures was higher when proximal filling was higher. However, cases of prosthesis with fractures did not present with radiographic appearance after 12 months that was worse than those femurs that were not fractured.

We found the ABG cementless hip has excessive acetabular wear and premature failure due to osteolysis.

In 60 patients implanted at mean age 56 years, 66 hips (mean follow up 48 months), 7 were revised and 7 have severe acetabular osteolysis. In some this is entirely asymptomatic. There was significant association with osteolysis, length of follow up and wear but no correlation between wear and acetabular component position, age, liner thickness, and use of ceramic or CoCr heads.

We recommend regular lifelong radiological review of these hips and suspension of use of this prosthesis until a wider review is undertaken.

Delayed sciatic nerve palsy is uncommon after primary hip replacement. Two kinds of sciatic palsy have been reported with regard to the time of onset: early palsy related to wound haematoma or lumbosacral nerve elongation which occurs between surgery and 18 days, is more frequent than delayed palsy, occurring between 10 and 32 months, which is usually caused by cement extrusion or heat produced by cement polymerisation.

We present two cases of delayed, transient sciatic nerve palsy arising at three weeks and four months after primary cementless arthroplasty, respectively, without haematoma and with a normal lumbar spine. These palsies were possibly caused by excessive tension from minor limb lengthening of 2 cm to 4 cm required to achieve leg-length equality. As the initial symptoms were limited to calf pain and mild numbness in the foot, surgeons should be aware of this mode of onset, particularly when it is delayed after hip replacement. Both patients recovered fully by 12 months after surgery so we did not undertake surgical exploration of the nerve in either patient.

We have studied the role of computerised axial tomography in the assessment of the acetabulum before an uncemented Mittelmeier arthroplasty was performed in 20 patients. In the absence of gross anatomical abnormality, computerised tomography did not provide additional information, but in eight patients it was useful in determining adequacy of acetabular depth, anterior acetabular cover, and thickness of the anterior and posterior walls. In these patients, the CT scans provided information which was not available from plain radiographs and greatly assisted in pre-operative planning.