[Dislocation of total hip endoprosthesis with special reference to various techniques]

1238 primary total hip replacements for arthritis were performed in our hospital from 1980 until 1988. 26 dislocations (2.1%) were registered during this period. No differences became obvious regarding age, sex, type of prosthesis and different concepts of postoperative treatment. After the posterior approach dislocations occurred in 18 (3.1%) of the cases, 8 dislocations (1.2%) were found after the transgluteal approach. The dislocation rate was significantly higher for the posterior approach. Derotation braces were not able to decrease the risk of redislocation. Most of the dislocations happened during the first postoperative week. The most frequent occasions were rotation of the operated leg while lying in bed and deep sitting positions. Performing the posterior approach for primary total hip arthroplasty the surgeon has to realize the higher dislocation rate.

[The Göttinger minipig as an animal model in hip endoprosthesis. Anatomy, anesthesia, operation results]

The Göttingen mini swine is a good experimental animal. The electrolytes and the bone healing rate is comparable to human. The weight of the animals should be 30-45 kg. All surgery is performed under endotracheal general anaesthesia without any complication. There is minimal blood loss because blood pressure is only 40/80 mmHg. We used the anterolateral approach. The feature peculiarity of this animal model are: 1. Skin incision should start 10 cm cranial to the tail and should be curved. 2. The osteotomy of the head is V-shaped in maximal external rotation. 3. The acetabulum is prepared with a 23.5 mm reamer. 4. The stem should be implanted first. After completion of the preliminary test operations, 10 animals were operated in the described standard manner. During one year follow-up there was only one radiological cup-loosening.

Acetabular supporting ring in total hip replacement

A series of 14 total hip arthroplasties with a Müller acetabular supporting ring including 3 primary and 11 revision arthroplasties is reviewed. This device was used in cases of acetabular bone deficiency, and bone graft was added in 11 cases. The mean length of follow-up was 39.9 months. Twelve patients had good or satisfactory results, while two operations failed. These results indicate that the acetabular supporting ring is a useful implant in cases with acetabular bone stock deficiency.

[Embolism and intramedullary femoral surgery]

All intramedullary femoral surgery entails embolic phenomena which explain peroperative collapses formally known as bone cement implantation syndrome, as well as perioperative fat embolism syndromes. Locally, the bigger the cavity is, the higher the number of accidents: 2.5-5 per cent for GUEPAR hinged-knee prosthesis, 1.75 per cent for total hip arthroplasty with long stem, and 0.1 per cent during classic THA with cement limited to the metaphysis. Anomalies in bone vascularization also increase risk: 10.5-13 per cent during prophylactic nailing for shaft metastases, 1-11.5 per cent during hemiarthroplasty cemented in osteoporotic bone of femoral neck fractures, and only 0.1 per cent during THA implanted because of arthrosis. Not only cement, but also rods, reamers, nails, implants, ultrasonic tool for cement extraction, increase the pressure inside the cavity. Methylmethacrylate is no longer the only incriminated factor, even if it is responsible for a major part of the compressive load. The intensity and duration of the pressure are correlated with the number of embolic phenomena and with measured cardiopulmonary parameters. The intracavity fat content is expelled (an empty cavity, as in THA revision, does not lead to embolic phenomena). Then filters through the intraosseous veins whose diameter limit the size of the extruded embolic phenomena. The ultrasonography of the inferior vena cava shows innumerable fine particles and thrombi which are already organized under the influence of procoagulant factors released from the operative shield and which remain crumbly. These emboli cross the cardiac cavities. Transesophageal echocardiography (TEE), of recent use, does quantify the amount of right atrial filling, duration of echogenesis and size of particles: the result is higher in patients who underwent cemented versus noncemented THA: however the embolism score is no an indicator of seriousness because it is not correlated with cardiorespiratory manifestations; TEE shows only one fourth of the patent foramen ovale, whereas the atrial septal defect is surely one of the most efficient systemic invasion mechanisms to produce perioperative fat embolism. Lung response is most often asymptomatic, even if all patients undergoing intramedullary surgery display an increase in pulmonary vascular resistance which is managed by the right heart only, as well as pulmonary (and sometimes systemic) microvascular fat obstruction. Common operating room monitoring procedures do not detect successive embolic phenomena before they cause pulmonary arterial hypertension which then has repercussions on the left heart and in turn causes peroperative hemodynamic accidents. Only pulmonary arterial pressure measurement with a Swan-Ganz catheter gives early and durable signs of an intolerance to embolic load. Preventive treatment is surgical as there is an inverse relation between embolic marrow and marrow eliminated by large volume washes (which is often more effective than draining). Cement indications in older patients as well as the choice of fixation techniques in femoral fractures must take into account the cardio-pulmonary condition of the patient. Resuscitation procedures dealing with these complications end in the patient's death in half of the cases.

Results of the Müller acetabular reinforcement ring in revision arthroplasty

Between April 1984 and December 1987 a Müller acetabular reinforcement ring was employed in 98 revision cases (94 patients). Twenty-two patients died before follow-up evaluation. Forty-seven (66%) of the remaining 72 patients (49 of 75 hips) were examined after a mean of 6.4 years (range 5-9 years). Excluding those who died, the postoperative outcome of 69 patients is known. Migration was measured according to Sutherland by means of a digitising table. Cup position was determined by a new angle (beta) between the sacroiliacal line and a reference line. The reference line connects the centre of the femoral head with the intersection between the sacroiliacal and obturator lines. Aseptic and septic loosening required revision surgery in 2 cases each (4%). The postoperative beta angle showed a high correlation with migration (P = 0.001) as well as with radiolucencies (P = 0.001). In cases which required further revision, beta amounted to 44 deg (craniolateral position), and in stable cases up to 60 deg. A lateral and cranial position of a Müller acetabular reinforcement ring leads to high loosening rates. The beta angle accurately describes cup position, and its postoperative value is highly predictive for loosening.

Total hip arthroplasty in patients with avascular necrosis of the femoral head: a 2- to 10-year follow-up

One hundred twenty-three total hip arthroplasties were performed in 85 patients with osteonecrosis of the femoral head. There were 51 males and 34 females with an average age of 45 years. The average followup time was 4.6 years with a range of 2 to 10 years. All femoral stems and 71 sockets were fixed with acrylic cement. Fifty-two of the sockets used were placed without cement. The average Harris hip score improved from 45 points preoperatively to 92 points at the time of last followup. Of the 246 components used, 6 acetabular and 4 femoral prostheses in 7 patients have been revised (4%). Two components (0.8%) were revised for infection, 2 (0.8%) for repeated dislocation, and 6 (2.5%) for aseptic loosening. There is current radiographic loosening in 3 acetabular and 2 femoral components (2%). None of the noncemented acetabular components was either radiographically loose or revised. Within the subset of the 36 patients (52 hips) with a minimum 5-year followup (average, 6.6 years), 5 components (5%) were revised and 4 (4%) components are radiographically loose. The overall revision rate for cemented and hybrid hips at 2 to 10 years followup was 4%. The revision rate for hybrid hips alone was 2.5% in the entire series and 2% for hips with a minimum followup of 5 years. These results seem significantly better than previously reported. Using modern cement techniques and components, total hip arthroplasty can give excellent results in the young patient with avascular necrosis and may be the treatment of choice when reconstructive surgery is required.

Charnley total hip arthroplasty with use of improved techniques of cementing. The results after a minimum of fifteen years of follow-up

Three hundred and fifty-seven consecutive Charnley total hip arthroplasties were performed in 320 patients with use of a so-called second-generation technique of cementing between July 1976 and June 1978. This technique includes use of a distal femoral intramedullary cement plug, hand-mixing of the cement, and use of a cement gun to deliver the cement into the femoral canal in a retrograde fashion. At the time of the latest follow-up evaluation, a minimum of fifteen years after the arthroplasty, 130 patients (142 hips) were still alive, 189 patients (214 hips) had died, and one patient (one hip) had been lost to follow-up. A radiograph was made for 116 (82 per cent) of the 142 hips in the 130 surviving patients. Of the 356 hips that had not been lost to follow-up, thirty-three (9 per cent) had had a revision and two (1 per cent), a Girdlestone resection arthroplasty during the follow-up period. Nineteen hips (5 per cent) were revised because of aseptic loosening of the femoral or acetabular component, or both (two hips); seven (2 per cent), because of loosening with infection; and seven (2 per cent), because of dislocation. The two resection arthroplasties were performed because of loosening with infection; both were done in patients who died before the time of the latest follow-up evaluation. Of the 142 hips in the 130 patients who were alive at a minimum of fifteen years, twenty-two (15 per cent) had been revised: fifteen (11 per cent), because of aseptic loosening; three (2 per cent), because of loosening with infection; and four (3 per cent), because of dislocation. Revision of the femoral component because of aseptic loosening (excluding components that were revised because of dislocation or infection) was performed in four (1 per cent) of the entire series of 356 hips and in three (2 per cent) of the 142 hips in the 130 patients who survived for at least fifteen years. Two of the 356 hips and two of the 142 hips had aseptic loosening of the acetabular as well as the femoral component at the time of the revision. Loosening of the femoral component, defined as aseptic loosening leading to revision or as definite or probable radiographic loosening, occurred in ten (3 per cent) of the 356 hips and in six (5 per cent) of the 116 hips for which radiographs were made at a minimum of fifteen years. The acetabular component was revised because of aseptic loosening in seventeen (5 per cent) of the entire series of 356 hips and in fourteen (10 per cent) of the 142 hips in the 130 patients who survived for at least fifteen years. The acetabular component loosened without infection in forty-one (12 per cent) of the 356 hips and in twenty-six (22 per cent) of the 116 hips for which radiographs were made at a minimum of fifteen years. In two of these patients, the femoral component was also revised. Thus, of the entire series of 356 hips, two had a revision of the femoral component alone because of aseptic loosening; fifteen, a revision of the acetabular component alone; and two, a revision of both components. Of the 142 hips in the 130 patients who survived for at least fifteen years, one was revised for loosening of the femoral component alone; twelve, for loosening of the acetabular component alone; and two, for loosening of both components. These findings demonstrate long-term durability of fixation of the femoral component but less reliable fixation of the acetabular component, even when the surgeon is experienced and improved techniques of cementing are used.

[Long-term results after Charnley hip replacement]

We made a prospective study of 241 Charnley total hip replacements performed between 1968 and 1974. In 1990 we reviewed 92 patients with 103 hips or 96% of surviving hips at a mean follow-up of 17.6 years (15 to 20.6). The clinical results were excellent with Charnley scores of four or more for pain in 95% of the cases, for function in 73% and for movement in 93%. Of the whole series, 8.3% had been revised and Kaplan Meier survival analysis showed a probability of revision at 20 years of 10.7%. No significant difference concerning the results was found between young patients operated between the ages of 34 to 55, and older patients operated between the ages of 56 to 79 years. These results are similar to those from the few other series with extended follow-up and make it difficult to justify the present widespread use of uncemented hip prostheses.

Primary cementless hip arthroplasty with a titanium plasma sprayed prosthesis

One hundred two patients underwent 105 primary uncemented total hip arthroplasties and were reviewed at a minimum of 5 years after operation (mean, 6.1 years). The components were titanium alloy with a titanium plasma spray coating. The acetabular revision rate was 11.4%. Acetabular cavitary lytic lesions were identified in 25.5% at 5 years. All acetabular revisions were performed for a combination of wear and osteolysis. One femoral revision was performed to facilitate an acetabular revision, but the femoral revision rate for aseptic loosening was 0%. In addition, no femoral components had subsided or were thought to be loose radiographically. Thigh pain was present in 4% at 5 years. Despite the 25.5% incidence of acetabular osteolysis, distal femoral lysis was not seen and only 5% showed focal osteolysis in the trochanteric region proximal to the circumferential porous coating of the femoral component. Component design features were thought to be critical to the excellent performance of the femoral component and to the poor performance of the acetabular component.

Impacted graft incorporation after cemented acetabular revision. Histological evaluation in 8 patients

We took core biopsies from the acetabulum in 8 patients (at reoperation) after a previous revision with impacted cancellous allograft chips in combination with cement. Except for one biopsy specimen, the graft showed different stages of incorporation. In the specimens taken at 4 months, revascularization of the graft was found. Osteoclasts had removed parts of the graft, while woven bone had formed on the remnants of the graft and in the stroma that was invading the graft. Subsequent specimens showed that this mixture of graft and new bone was in due time remodeled into a normal trabecular bony structure with viable bone marrow that contained little or no remnants of the original graft. The graft-cement interface was present in 4 biopsies taken at 1, 22, 28, and 72 months. The specimen obtained 28 months after revision showed vital bone locally in direct contact with the cement layer; however, a soft tissue interface predominated.

Hybrid total hip arthroplasty: 7- to 10-year results

One hundred fifty consecutive hybrid total hip arthroplasties in 139 patients were performed using an uncemented hemispheric porous coated acetabular component (HGP-I) with screws and a femoral component (Precoat) cemented with contemporary cementing technique. The average patient age was 67 years (range, 39-85 years). No patients were lost to followup. Eighty-six patients (91 hips) were alive for an average clinical followup of 103 months (range, 84-127 months); 81 hips had corresponding radiographic analysis. The average Harris hip score preoperatively was 47 points and increased to 88 points at followup. Ninety-five percent of patients had absent or slight pain. Aseptic loosening occurred in 2 femoral components (1.3%), 1 of which was revised for secondary osteolysis. Both hips had suboptimal cement mantles (C-2 or D grades). No femoral osteolysis was seen in stable components. Two acetabular components migrated; 1 secondary to preoperative irradiation osteonecrosis and 1 secondary to a bulk autogenous graft. Acetabular osteolysis without loosening developed in 2 patients (1.3%). Using revision and radiographic loosening as the end point, the probability of both components surviving 10 years was 96.9%, 98.6% for the acetabular component, and 98.4% for the femoral component. These results show that hybrid total hip arthroplasty offers excellent clinical function and exceptional 10-year survivorship.

Hybrid total hip replacement: rationale and intermediate clinical results

The decade of the 1980s was considered by many hip surgeons to be the decade of cement versus cementless. An alternate approach was introduced in which the acetabular component used was cementless and the femoral component was fixed with cement. This has been called the hybrid total hip replacement. The rationale for this approach is presented and intermediate term results (average, 6.6-year followup) showed that among 65 consecutive standard hybrid total hip replacements in patients who had an average age of 61 years (range, 23-83 years) at the time of surgery, no femoral component was revised for aseptic loosening and no acetabular component was revised for aseptic loosening. Of the 130 components, 3 were removed in 2 patients. One patient had both components removed because of recurrent dislocation and 1 patient had the acetabular component revised because of failure of fixation of the polyethylene liner. The clinical results of this approach were excellent in the intermediate term and may have promise for the long term.

The Wagner revision stem for severe osteolysis. 31 hips followed for 1.5-5 years

We used the Wagner (1989) method in 31 hip revisions because of loosening with pronounced scalloping, which made a conventional revision unsuitable. The radiographs showed that within a few months new bone developed in the defects. In 5 cases, a new revision was necessary at an early stage, because of dislocation and/or subsidence. At follow-up after 3 (1.5-5) years, 21 of the remaining 26 hips were pain-free and 23 had almost full range of motion.

Trochanteric osteotomy and wire fixation: a comparison of 2 techniques

Between 1986 and 1989, 190 patients (214 hips) with the diagnosis of osteoarthritis or posttraumatic arthritis underwent cemented Charnley total hip replacement surgeries via the biplane or single plane transtrochanteric approach. The technique of surgery was identical in every aspect except for the technique of the trochanteric osteotomy and reattachment. The results indicate that there was no significant difference in union rates between the 2 groups. Six (6.4%) patients in the biplane group and 7 (6.2%) patients in the single plane group had obvious evidence of nonunion at the 1-year evaluation. This study suggests no significant difference in union rate between a group of patients with biplane osteotomy and a closely paired group of patients with single plane osteotomy. Other equally important factors also may influence the rate of union of the trochanter in total hip arthroplasty.

Hybrid primary total hip arthroplasty: a 5- to 9-year followup study

One hundred fifty-two hips were reviewed at a minimum of 5 years after hybrid primary total hip arthroplasty using uncemented porous coated acetabular components and cemented femoral stems to determine the intermediate term durability of this method of fixation. Five hips (3.6%) have been revised: 1 for dislocation (0.7%), 1 for cup loosening (0.7%), and 3 for femoral loosening (2.2%). Clinical results proved to be extremely reliable in this series with 78% of the patients reporting no pain and 19.7% reporting slight or occasional pain. Radiographic evidence of polyethylene wear was evident in more than 1/2 of cups, but significant osteolysis or component loosening was not commonly seen on the cup side. On the femoral side incomplete radiolucencies were present in 31%, and focal osteolysis in 12.2%, nearly always proximally in Zones 1 and 7. These intermediate term results compare favorably on the femoral side and very favorably on the acetabular side to prior reported series. These results support the continued use of this combination of fixation methods for primary arthroplasty, but polyethylene wear and its effects remain a concern regarding the long term performance of these arthroplasties.

Treatment of periprosthetic fractures around total hip arthroplasty with an extensively coated femoral component

Late periprosthetic fractures may occur around loose cemented femoral components, usually as a consequence of osteolytic bone deficiency. The management of these fractures should include revision total hip arthroplasty using techniques that achieve fracture healing and component stability. If a cementless component is to be used, osseointegration is desirable. Presented herein is a technique of revision total hip arthroplasty for this injury using a curved, extensively coated femoral component. Four cases have been followed for a minimum of 2 years. Each case achieved a good or excellent clinical outcome while radiographs demonstrated fracture healing and osseointegration.

The Otto Aufranc Award. Skeletal response to well fixed femoral components inserted with and without cement

Previous studies evaluating femoral remodeling after total hip arthroplasty have used clinical radiographs and dual energy xray absorptiometry. Limitation of these techniques make it impossible to quantify the magnitude of bone loss in terms of cortical thinning and cortical bone area and bone mineral density changes. Femoral cortical bone remodeling after cemented and cementless replacement was quantified and possible determinants of bone remodeling in terms of clinical and radiographic variables were evaluated. Forty-eight anatomic specimen femora from 24 patients with unilateral cemented and cementless hip replacements were analyzed. Cortical thickness, cortical bone area, and bone mineral density was assessed in 4 quadrants at 5 discrete levels. The maximum cortical bone loss by level was at the middle section for the cemented femurs and at the midproximal and middle sections for the cementless femurs. However, if one examines individual quadrants, the proximal medial cortex still represents the specific region of maximal bone loss for both types of implant fixation. The posterior cortex had substantially more bone loss, even in the diaphyseal levels, than had been previously appreciated. A strong correlation was noted between the bone mineral density of the control femur and the percentage decrease of bone mineral density in the remodeled femur. Based on this data, it seems that the less dense the bone is before hip replacement surgery, the greater the extent of bone loss after total hip arthroplasty regardless of the fixation type.

Hybrid total hip arthroplasty: a 7- to 11-year followup

A consecutive series of 125 hybrid total hip arthroplasties were performed in 120 patients by a single surgeon and were observed for an average of 8.6 years (range, 7-11 years). There were 38 men and 82 women with an average age of 71 years (range, 25-87 years) at the time of surgery. The diagnoses included primary and secondary osteoarthritis in 112 patients, osteonecrosis in 5 patients, and rheumatoid arthritis in 3 patients. All acetabular components were modular and had a Ti shell fixed with an average of 3 screws. The cemented femoral component was either Precoat or Precoat Plus with a 28-mm modular CoCr femoral head. The patients were prospectively observed clinically using the Harris hip score and radiographically using the Hip Society methods. Of the 125 total hip arthroplasties, 123 were followed for the entire observation period. The average preoperative Harris Hip Score was 37 (range, 15-55) and at the latest followup was 92 (range, 65-100). One acetabular component was revised for recurrent dislocations 3 years after surgery, and 1 stem was revised for mechanical loosening and 1 stem was radiographically loose. There was no evidence of cup migration of more than 1 mm. There were no radiolucencies around any of the screws. Two sockets had polyethylene wear of 2 mm. Localized pelvic osteolysis was noted in 5 hips (4%). The results of this study suggested that hybrid total hip replacement is an excellent procedure for reconstruction of the arthritic hip with minimal evidence of polyethylene wear and pelvic osteolysis.

A study of the factors in hip replacement dislocation. Part 2

Dislocation is a dramatic and distressing common complication following total hip replacement. The first article describing this study, published last week, considered some of the factors thought to predispose to dislocation. The authors emphasised the multifactorial nature of hip replacement dislocation and in this second article they examine the factors relating to acetabular position and orientation, and femoral component placement.

Nerve injury after posterior and direct lateral approaches for hip replacement. A clinical and electrophysiological study

Nerve injury is a rare complication of total hip replacement which may be related to the exposure used for the operation. The posterior approach is traditionally associated with injury to the sciatic nerve. We have compared the incidence of nerve injury after primary total hip replacement (THR) using either a posterior or a direct lateral approach. We studied 42 consecutive patients undergoing primary total hip replacement. The surgeons used a posterior (22 patients) or direct lateral (20 patients) approach in accordance with their normal practice. The obturator, femoral, posterior tibial and common peroneal nerves were assessed clinically and electrophysiologically by electromyography (EMG) and measurement of the velocity of nerve conduction before operation and at four weeks after. All patients were free from symptoms of nerve injury after operation but five lesions were identified in four patients by the electrophysiological studies; the obturator nerve was involved in two, the femoral in one, the common peroneal in one and the posterior tibial in one. All these injuries occurred using the lateral approach. Clinical assessment alone underestimates the incidence of nerve injury complicating THR. Our study does not confirm the association of nerve injury with the posterior approach which had been described previously.

Femoral canal occlusion in total hip replacement using a resorbable and flexible cement restrictor

We have investigated the use of a conically-shaped cement plug made of Polyactive (PA), a biodegradable copolymer. The flexibility and hydrogel properties were thought to facilitate occlusion of the femoral canal even when it was oval or irregular in shape. The function of the plug was first compared with that of the Thackray polyethylene model in 16 artificial plastic femora. The maximum intramedullary pressure achieved during cementing was ten times higher with the biodegradable model. Migration or leakage of cement did not occur when the diameter of the femoral canal was equal to or smaller than the diameter of the plug. We also showed that the biodegradable properties of this implant were such that it did not require removal during revision. The new plug was tested in a pilot clinical trial. At two years only two out of 21 patients had evidence of migration or leakage of cement, probably due to a mismatch in the size of plug and femoral canal. There were no local changes in the femur.

Avascular necrosis of the femoral head after allogenic bone-marrow transplantation. A retrospective study of 27 consecutive THAs with a minimal two-year follow-up

After an allogenic bone-marrow transplant, avascular necrosis of the femoral head may affect young adults, producing destructive lesions which require hip replacement. We have reviewed 27 consecutive such total hip arthroplasties (THA) at a minimal follow-up of two years. Of these, 20 were primary operations for Ficat (1985) stage-III and stage-IV lesions, and seven were revisions after the failure of previous surgery. The median age at operation was 30 years (17.5 to 44). The prostheses had a cemented, collared titanium-alloy stem, an alumina-alumina joint, and a press-fit socket. Seven had a titanium-alloy metal back and 20 had all-alumina cups of which six had to be cemented. At an average follow-up of five years, no patient had been lost to follow-up. One had died from septicaemia after two years and another with chronic graft-versus-host disease developed a deep infection 2.5 years postoperatively and had a successful revision. There were no revisions for aseptic loosening. The clinical results on the Merle d'Aubigné++ and Postel (1954) scale were very good or excellent in 23 hips (88%), good in one and fair in two. Ten hips showed incomplete acetabular radiolucencies less than 1 mm thick, but there were no radiolucent lines around the stems. We conclude that for these difficult patients THA with ceramic joints and careful technique provides the best short- and medium-term option after the failure of medical treatment.

Early outcome of total hip arthroplasty using the direct lateral vs the posterior surgical approach

A consecutive series of 49 patients who had a primary total hip arthroplasty (THA) for osteoarthritis is reviewed to determine the difference in clinical outcome between the direct lateral and the posterior surgical approaches to the hip. Group 1 comprised 28 patients off had THA by the same surgeon using a posterolateral approach. Group 2 comprised 21 patients who had THA using the direct lateral approach, modified from Hardinge. The improvement in the limp, abductor strength, Trendelenburg test, and range of motion over time was similar in the two groups. The average Harris hip score at 1 year was 90 for Group 1 (posterior approach) and Group 2 (lateral approach). At 2-year minimum follow up, the Harris hip score was 94 for both groups. Radiographic review showed that the incidence and severity of heterotopic bone was also similar for both groups. The authors conclude that the clinical and radiographic outcome for THA using the posterior and the lateral approaches to the hip yield similar clinical results.

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 formation 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.

[Pseudarthrosis of the proximal femur]

Mechanical and biological factors are responsible for non-unions of the proximal femur. We analyse the causal treatment-possibilities of the different localisations. Fifty-five patients with non-unions of the femoral neck (average age 53 years) with or without preexistent femoral head necrosis (44%) were treated by abduction osteotomy and followed up at regular intervals. In 15% of cases a second operation was necessary after an average of 9.3 years, including the early complications. At the latest control 90% of the patients were satisfied, with an average Harris hip score (HHS) of 91. The survivorship analysis with end point total hip replacement is favourable. In the same period 22 patients were treated with a total hip replacement. The 11 survivors had a clearly worse HHS of 65. The low-risk, technically demanding valgization osteotomy should be the first step in the treatment of femoral neck non-unions, even in the presence of femoral head necrosis; secondary operations are not compromised. Pertrochanteric non-unions are rare. The pertrochanteric fragment very often heals, leaving a lateral femoral neck non-union which can be treated with valgization osteotomy. Depending on the type of non-union and the age of the patient, anatomical reduction, medial displacement and valgization osteotomy can be employed. With the angulated plates of the ASIF (95 degrees, 120 degrees, 130 degrees) 23 of the 24 non-unions could be healed in one operation. Fourteen patients underwent total hip replacement. In the subtrochanteric area mechanical and vascular instability leads to implant failure or fatigue fracture. Rigid compression-re-osteosynthesis is the therapy of choice, the 95 degrees condylar plate the implant. Twenty-three of our documented 24 subtrochanteric non-unions healed, 4 in the presence of an infection. Multiple operations have been necessary in 2 of the 4 non-unions following a pathological fracture.

Long-term comparison of Charnley and Stanmore design total hip replacements

We reviewed the records of the long-term outcome of 208 Charnley and 982 Stanmore total hip replacements (THR) performed by or under the supervision of one surgeon from 1973 to 1987. The Stanmore implant had a better survival rate before revision at 14 years (86% to 79%, p = 0.004), but the difference only became apparent at ten years. The later Stanmore implants did better than the early ones (97% to 92% at ten years, p = 0.005), the improvement coinciding with the introduction of a new cementing technique using a gun. Most of the Charnley implants were done before most of the Stanmore implants so that the difference between the results may in part be explained by improved methods, but this is not the complete explanation since a difference persisted for implants carried out during the same period of time. We conclude that improved techniques have reduced failure rates substantially. This improvement was much greater than that observed between these two designs of implant. Proof of the difference would require a very large randomised controlled trial over a ten-year period.

Cement-within-cement revision hip arthroplasty; should it be done?

The complete removal of the cement mantle at revision arthroplasty can be extremely difficult. Some authors advise a 'cement-within-cement' revision technique in which a new layer of cement is applied to the old before insertion of the femoral component. We could find no long-term clinical data regarding the success of this procedure. In a simple biomechanical study, we examined the strength of the cement-to-cement interface in conditions likely to prevail in vivo. We found that the presence of a thin layer of blood and marrow debris at the interface weakened the cement-to-cement bond by 80% to 85%. These biomechanical findings and additional photomicrographic evidence do not support the practice of cement-within-cement revision arthroplasty.

Acetabular reconstruction in total hip revision using a bone graft substitute. Early clinical and radiographic results

Thirty revisions were performed on loose total hip replacements with a specific acetabular reconstruction technique combining the use of a bovine bone substitute and a support ring. One patient died of a cause unrelated to the procedure. No migration of the acetabular implant or bone lysis of the heterograft was seen in 27 cases after 3 years. Radiologically, the heterograft gradually condensed, and its appearance matched that observed with an allograft. The 2 failures with implant migration and heterograft lysis were interpreted as technical errors related to the use of the Müller ring. In both cases the Müller ring was supported by the cancellous heterograft and not by the host bone.

Impacted particulate allograft for femoral revision total hip arthroplasty. In vitro mechanical stability and effects of cement pressurization

The initial migration and micromotion of the revision femoral stem stabilized with morselized impacted cancellous allograft and bone-cement and the influence of cement pressurization on fixation of the cement/allograft composite to the host were examined with human cadaver femurs. The stability of the allograft/cemented reconstruction was found to be intermediate between those of conventional cemented and cementless stems. In most cases, the stability of the reconstruction was closer to that of cemented than to that of cementless stems. This may account for histologic findings of graft incorporation in experimental and retrieved specimens reported by other authors. Although increased cement pressurization led to greater penetration of cement into the graft bed, greater cement penetration did not increase fixation strength of the cement/allograft composite to the host.

Bipolar femoral head arthroplasty in osteoarthritis. A prospective study with a minimum 5-year follow-up period

Primary bipolar femoral head arthroplasties performed on 100 osteoarthritic hips were studied to a minimum of 5 years after surgery. All arthroplasties were performed on physically active patients. At a mean follow-up period of 5.5 years, The Hospital for Special Surgery hip scores were good to excellent in 96 hips. Transient startup soreness constituted the most frequent complaint, occurring in 34 hips. Three hips had more persistent pain localized to the acetabulum, necessitating revision to fixed sockets, which alleviated the symptoms. Four additional hips, in heavy, active men, developed polyethylene fatigue fracture and component disassembly. Acetabular migration of more than 5 mm developed in one hip. Motion, as determined radiologically, occurred primarily at the inner bearing. There were no dislocations or infections in the series. The Bateman bipolar prosthesis provides generally good results in osteoarthritic hips. The shorter operating time and the case of revision are special advantages of bipolar devices. Start-up soreness and stiffness is a shortcoming in approximately one third of cases. Component disassembly in heavy, active men is a problem and the bipolar arthroplasty should be avoided in these patients. Start-up soreness was a significant problem in particular.

Results of the total bi-metric cementless hip arthroplasty

A 2.9-year follow up of 50 primary Bi-Metric System cementless, porous-coated hip arthroplasties (Biomet) is presented. Four patients were operated bilaterally. In two patients, revision arthroplasty was carried out, in one because of infection, in the other because of loosening of the stem. The average Harris hip score was 96 points. The pain level according to d'Aubigné was 5.87. All patients belonged to Jensen's social function group 1. According to Engh's x-ray score, the femoral component achieved an average total of 19 points. Twenty-three patients with heterotopic ossification were graded according to Brooker et al; 18 patients belonged to group I-II, and 5 patients to group III. Discrepancy of leg length was measured in 20 patients, and averaged 0.52 cm (range: 0 cm to 2.5 cm). Four patients complained of thigh pain, but they had no radiographic evidence of loosening of components. The mean age was 63.4 years for women and 58.1 for men. Acceptably high Harris Hip Scores were obtained for the Bi-Metric hip prosthesis at 2-year follow up.

Cementless total hip replacement does not change bone mineral density of the lumbar spine, DEXA measurements in 50 patients

We measured the lumbar spine mineral density with the dual-energy x-ray absorptiometry method, 8 days, 3 and 6 months after total hip replacement in 50 patients and found no statistical differences over time.

Use of iliofemoral distraction in reducing high congenital dislocation of the hip before total hip arthroplasty

The iliofemoral distraction with Wagner's apparatus was conducted in 20 adult patients with untreated unilateral congenital dislocation of the hip (Crowe group IV) before total hip arthroplasty. During the distraction period of 8 to 17 days, this technique had effectively reduced high dislocation of 4.5 cm (range, 3.5-5 cm). No pin-tract infection was encountered. Surgical difficulties in total hip arthroplasty for these patients were reduced. Potential problems, such as irreducibility, overshortening, nerve palsy, and displaced femoral fractures, were avoided. At an average follow-up period of 43 months (range, 25-63 months), all patients have excellent or good results, with an average Harris hip score of 94.3 (range, 84-100). Leg length was restored. The iliofemoral distraction is valuable prior to difficult total hip arthroplasty for high dislocation.

Cemented revision total hip arthroplasties in patients younger than 55 years old. A multicenter evaluation of second-generation cementing technique

The results of all cemented first-time revisions in Sweden performed in patients younger than 55 years of age, during the period 1984-1986, are reported. The revisions were performed by the average orthopaedic surgeon in 25 hospitals distributed throughout Sweden. Second-generation femoral cementing technique was used. One third of the acetabular revisions were performed with pressurized cement. The reason for revision was aseptic loosening. Seventy hips in 68 patients were reviewed at an average follow-up period of 7 years (range, 4-10 years). The average age of the patients at the time of revision surgery was 47 years. Forty-eight cups and 57 stems were revised using cement. Survival analysis, with revision for aseptic loosening as the endpoint, suggests an overall 76% survival rate after 8 years. The survival rate for the cup was 80%, and for the stem, 85%. The radiographic evaluation revealed that the cement mantle was inadequate in many revisions. Localized osteolysis was rare. Clinical data were reported for 55 (53 patients) non-revised hips. Thirty-five hips were without pain or slightly painful. Forty patients limped when walking. Forty-three patients were satisfied with the revised hip. These results using second-generation femoral cementing technique are better than those reported with first-generation technique, but the failure rate in this young patient population is too high. The search for a more durable fixation in revision total hip athroplasty for young patients with long life expectancy is ongoing. These results emphasize that there is a need for centralization to gain experience in extended clinical research and to further improve surgical and cementing techniques.

Metal on metal surface replacement of the hip. Experience of the McMinn prothesis

The historical failure of surface replacement has been due to the production of wear debris with subsequent bone resorption, loosening, and failure. To avoid these problems, a surface replacement using a metal on metal bearing allowing thin components and femoral design and instrumentation to avoid varus alignment has been designed. Two hundred thirty-five joints have been resurfaced with this prosthesis in almost 5 years. There have been no femoral neck fractures and no dislocations. There have been 4 designs differing in the method of fixation. In the press fit group, 6 of 70 hips had to be revised for aseptic loosening. In the cemented group, debonding of the cup occurred in 3 of 43 cases. Six patients had hydroxyapatite coated components and have had excellent clinical outcomes. The current design uses a peripherally expanded hydroxyapatite coated cup and a cemented metal head; 116 of this design have been implanted during a 19-month period with excellent outcome. Despite short followup the authors are hopeful that the combination of a polar metal on metal bearing with appropriate fixation will yield a method of preserving bone stock in the younger patient requiring arthroplasty.

Bipolar hip replacement in sickle cell disease

A retrospective study is presented of 26 uncemented bipolar hip replacements for avascular necrosis of the femoral head due to sickle cell disease which were carried out between 1987 and 1992. All patients were treated according to a protocol. The average follow up was 4.6 years (range 2.1 to 7 years). After operation, the average Harris hip score improved from 36 to 88. Bone culture was positive for bacterial growth in 4 hips (coagulase negative staphylococcus in 3). There was progressive wear of acetabular articular cartilage in 2 cases, but no clinical or radiological evidence of loosening of the femoral stem. Seventeen complications occurred in 9 of the 21 patients (5 in one patient). A longitudinal split of the femur was the commonest operative complication and occurred in 5 hips. Femoral medullary sclerosis was seen in 8 cases. Patients with sickle cell disease have a high risk of complications, but this type of hip replacement should be considered in carefully selected patients who have avascular necrosis of the femoral head.

The omega lateral approach to the hip

We describe a modified lateral approach to the hip which exploits the function continuity of gluteus medius and vastus lateralis and their dense crescentic attachment to the greater trochanter. The gluteus medius is not incised or split, but is detached and mobilised with gluteus minimus as one unit. This facilitates reattachment of the glutei and helps to preserve abductor function.

The bone-implant interface of femoral stems with non-circumferential porous coating

A histological study was performed of the bone-implant interface of fifteen titanium-alloy femoral stems with porous coating limited to three proximal areas that did not cover the full circumference of the device. The specimens were obtained at autopsy from ten cadavera at a mean of forty-six months (range, one to eighty-nine months) after the implant had been inserted without acrylic cement. The volume fraction of bone within the porous spaces (the percentage of the porous space that was filled with bone) and the extent of bone ingrowth (the percentage of the porous-coated surface covered with in-grown bone that was more than one-half fiber-diameter deep, as measured from the outer surface of the porous coating), were determined with histomorphometric methods. Eleven of the fifteen stems had bone within the porous coating that was in continuity with the surrounding medullary bone. The mean volume fraction of bone ingrowth in these specimens was 26.9 per cent (range, 12.2 to 61.0 per cent), and the mean extent of bone ingrowth was 64.3 per cent (range, 28.6 to 95.2 per cent). Both of these parameters increased with time. In the other four stems, the bone lacked continuity with the surrounding trabecular bed. Two of these stems had a limited amount of bone within the porous coating, and two stems (from one patient) had no bone ingrowth. Periprosthetic membranes surrounded by a shell of trabecular bone covered the uncoated surfaces of the stems. The membranes of implants that had been in situ for eight months or more demonstrated polyethylene wear debris, and other particles generated at the level of the joint, within histiocytes throughout the length of the femoral stem.

CLINICAL RELEVANCE

The findings in this study are relevant to the utilization and mechanisms of failure of femoral stems inserted without cement. Bone ingrowth and the resulting stability of the implant can be achieved with porous-coated stems. However, the extent of the surface that is porous-coated must be sufficient to prevent trabecular fracture as a secondary mechanism of loosening. Interruptions in the circumferential extent of the porous surface are associated with the formation of periprosthetic membranes, which provide a pathway for migration of particulate wear and corrosion products to the distal part of the stem. A circumferential coating may retard the access of particles and thus decrease the possibility of diaphyseal osteolysis.

Bilateral total hip arthroplasty: one stage versus two stage procedure

The purpose of this study was to determine if any differences existed in the early complication rate, short term clinical outcome, and total length of hospital stay between patients who had bilateral total hip arthroplasty performed under a single anesthetic (during 1 patient visit to the operating room) and patients who had the procedure performed under 2 anesthetics (during 2 patient visits to the operating room). Patients operated on bilaterally were divided into 3 groups: Group A (1 stage procedure)--hips that were operated on simultaneously (128 hips); Group B (2 stage procedure)--surgeries performed less than 6 weeks apart (126 hips); and Group C (2 stage procedure)--surgeries performed between 6 weeks and 6 months apart (256 hips). All patients were evaluated after an average followup of 1.5 years. There were no differences in operative, early local, or general complications among the 3 groups. In particular, no higher incidence of pulmonary embolism or deep vein thrombosis was found in the 1 stage group. Preoperatively, very stiff hips (total range of motion < 50 degrees) gained significantly more motion in the 1 stage group than in the 2 stage groups, whereas hips with better preoperative motion (total range of motion > 50 degrees) improved the most in Group B, without a significant difference occurring between Groups A and C. The degree of pain reduction was the same in all groups, but patients in the 1 stage group had a significantly better capacity for walking after their procedure. Average total hospital stay was 5 to 6 days less for the patients in Group A than those in the other groups, which, combined with using the operating room only once, resulted in a reduction of overall hospital costs by more than 30% when using the 1 stage procedure.

Varus migration of PCA stems

Forty-seven patients with cementless, porous-coated anatomic hip replacements were evaluated after a minimum 2-year follow up with specific attention to varus migration of the stem. A cadaver study was done to define a relationship between projected size of the lesser trochanter seen radiographically, rotation of the femur, and stem position. Seven (15%) of the stems migrated into varus with the distal tip moving laterally. Thigh pain occurred in patients with varus migration and those with no change in stem position. A lower percent canal fill was seen on the lateral radiograph (P < .001) and larger average width of radiodense lines in zone 1 superolateral, and zone 6, midstem medial (P < .005) in the patients with varus migration. Poor distal stability associated with a lower percent canal fill at the stem tip seen on the lateral radiograph may result in varus migration.

The effect of superior placement of the acetabular component on the rate of loosening after total hip arthroplasty

A method for measurement of the true acetabular region and the approximate femoral head center as well as a classification consisting of four zones for assessment of the acetabular position of the acetabular cup were used to analyze the results of primary total hip arthroplasty with cement in 117 patients (145 hips). All patients had Crowe type-II congenital dysplasia of the hip. The mean age at the time of the arthroplasty was fifty-one years (range, fifteen to seventy-six years), and the mean duration of follow-up was fourteen years (range, two to twenty-two years). The initial position of the acetabular cup outside of the true acetabular region and outside of zone 1 (inferior and medial) was associated with an increase in the rates of loosening (p < 0.05) and revision (p < 0.04) of the femoral components. Cups that initially were more than fifteen millimeters superior to the approximate femoral head center, without lateral displacement, were associated with an increased rate of loosening (p < 0.001) and of revision (p < 0.04) of the femoral components as well as with an increased rate of loosening (p < 0.002) and of revision (p < 0.01) of the acetabular components. These findings suggest that superior positioning of the acetabular component, even without lateral displacement, leads to increased rates of loosening of the femoral and acetabular components. An attempt should be made to position the acetabular component in or near the true acetabular region.

How superior placement of the joint center in hip arthroplasty affects the abductor muscles

This study examines the effects of a superiorly placed hip center on the strength of the abductor muscles. A 3-dimensional computer model of the hip and the surrounding musculature was used to calculate the moment arms, forces, and moments generated when the hip abductor muscles are maximally activated. A representation of a hip prosthesis was implanted into the computer model with altered hip center positions and a range of prosthetic neck lengths. Analysis of these simulated hip replacements demonstrated that superolateral placement of the hip center (2 cm superior and 2 cm lateral) decreases the moment arms of the hip abductor muscles by an average of 28%. This decrease in moment arm cannot be restored by increasing prosthetic neck length, resulting in an unrecoverable loss of abduction strength with superolateral displacement. By contrast, a 2-cm superior displacement of the hip center changes the moment arms and force generating capacities of the abductors by less than 10% if prosthetic neck length is increased to compensate for decreased muscle length. The results of this study suggest that superior positioning of the hip center, without lateral placement, does not have major, adverse effects on abduction moment arms or force generating capacities when the neck length is appropriately increased.