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PubMed2005

Outcome of acetabular revision using an uncemented hydroxyapatite-coated component: two- to five-year results and review.

This is a retrospective review of 50 uncemented acetabular revisions with porous, hydroxyapatite-coated cups. The acetabulum alone was revised in 22 hips and both components were revised in 28 hips. The majority of hips (26) had type 2A (Paprosky) acetabular bone loss. All the revisions were carried out through a posterior approach. The mean duration of follow-up was 32 months (range, 24-52 months). Clinically, there was significant improvement in pain and moderate improvement in movement and mobility, and there is no radiological sign of failure of any cup so far. Re-revision was performed in 3 hips (6%) for recurrent dislocation. Our early results favor the use of this type of cup in acetabular revisions with moderate bone loss, but longer-term follow-up will be required. Key words: acetabulum, hydroxyapatite, revision, bone deficiency, complications.

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PubMed2006

The correlation between immediate radiolucent lines and early implant migration in cemented acetabular components.

Periacetabular radiolucent lines (RLLs) on postoperative radiographs have been associated with early loosening of the acetabular component. It has also been shown that excessive migration of an implant corresponds to an increased incidence of later clinical failure. This study relates RLLs on anterior-posterior hip radiographs taken 10 days and 6 months postoperatively to implant migration detected by roentgen stereophotogrammetric analysis. We have shown that RLLs in DeLee and Charnley zone III in the first week postoperatively as well as at 6 months are positively and significantly (P < .05) associated with migration detected by roentgen stereophotogrammetric analysis. No significant association was found for zone I or II at either 10 days or at 6 months. Considering the limitations in observing RLLs, their presence in zone III appears to reflect on the mechanical stability of the acetabular cup from the beginning. This indicates that zone III, which represents the inferomedial aspect of the acetabulum, might have to receive special attention when preparing the acetabulum and implanting the acetabular cup.

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PubMed2005

Contact pressures in the flexed hip joint during lateral trochanteric loading.

Acetabular fractures are an especially problematic outcome of motor vehicle side impacts. While fracture type has been correlated with impact direction and femoral orientation, actual contact pressures in the hip joint have not been quantified for lateral loading conditions. In the present study, we used pressure sensitive film to measure contact areas and pressures in seven hip joints from four cadavers under quasi-static lateral loading through the greater trochanter. The aim was to quantify the interactions of the femoral head with the acetabulum associated with variations in femoral orientation. Three angles of hip flexion (80 degrees , 90 degrees , 100 degrees ) and hip abduction (-10 degrees , 0 degrees , 10 degrees ) were tested, producing nine test orientations for each joint. We observed that contact areas, pressures, and forces varied significantly with femoral orientation for the adducted hip. The principal locations of load transmission were in the anterior and posterior regions of the acetabulum. For the abducted femur, contact pressures were concentrated anteriorly, and with increased adduction, anterior contact pressures diminished while posterior and superior pressures increased. The movement of pressure sites was consistent with mechanisms of acetabular fractures described by Letournel and Judet and provides new data for validation of finite element models of the pelvis in side impact.

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PubMed1995

Acetabular fractures.

Trauma injuries to the acetabulum and the associated pelvic region are second only to head injuries in mortality and morbidity for surgical patients. Surgeons in the past avoided exposing and stabilizing complex fractures of the acetabulum because of the intricate anatomy of the pelvic region. Recent advances in surgical techniques have increased the use of open reduction internal fixation of acetabular fractures. Early internal fixation of acetabular fractures allows rapid mobilization of severely injured patients and provides trauma patients optimal, long-term, functional results.

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PubMed1997

Statically equivalent load and support conditions produce different hip joint contact pressures and periacetabular strains.

The hip is a common site of orthopaedic trauma and disease, and considerable research has been directed toward understanding the development of contact pressures within the joint. Virtually all experimental studies to date have employed proximal femurs compressed along the joint reaction force vector into acetabulae explanted from cadaver pelves. This approach presumes that deformations of the acetabulum are highly localized, and that the pelvis is functionally a rigid body. We have developed a methodology that uses intact pelves loaded through simulation of the abductor mechanism. A direct comparison of the two techniques revealed significantly different joint contact characteristics and periacetabular strains. Fuji film measurements of contact area and pressure were more widely distributed across the acetabulum for the intact pelvis, with significant pressure development in anterior and posterior regions. Contact patterns in the explanted acetabulae were concentrated in the superior portion of the joint. Principal strains from three rosette gages placed near the acetabular rim were also significantly different for the two testing techniques, but were not substantially altered by the presence of Fuji film within the joint. The results indicate that deformation of the entire pelvis and the manner in which loads are applied significantly affect development of contact pressures within the hip joint, and that Fuji film is a suitable technique for recording those patterns.

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PubMed1997

The hip joint as a conchoid shape.

The hip joint is not an exact ball and socket joint. In a meridian section, the mean deviation from a conchoid shape is quite small, so that this shape might better describe the joint's shape. This conclusion was reached by measuring the cartilaginous and osseous shapes of eight normal hip joints (multiorgan donors with average of age 33 yr, range 19-46 yr) using a CNC coordinate measuring machine (CMM). On two additional hip joints, only the osseous shape was determined. A rotational axis was first determined by finding parallels of latitude at the femoral head and acetabulum. At the meridian sections, the best-fitting circle or conchoid was determined from the scanned measuring points, using least-squares regression. Two perpendicular meridians were then measured for each sample and used to evaluate the three-dimensional shape. The medium squared deviation showed a better fit for a conchoid shape compared to a sphere for all samples tested. Furthermore, the equation of the conchoid for the femoral head (r = a + b cos phi) and that for the acetabulum (r' = a' + b' cos phi) were related in that a = b' and b = a' within mean deviation factors of 4%. Their special shape makes the joint less likely to sublux compared to a ball and socket joint. In addition, the rolling and gliding mechanisms between the two shapes may result in less wear.

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PubMed1998

Modified cups.

Late results of structural allografting of the acetabulum are quite variable. In order to reduce or avoid the necessity for bone grafting, some modified cups have been developed. The deep cup with or without a lateralized polyethylene liner reduces the problem of the protrusio socket. Oblong or bilobed ingrowth cups significantly reduce the need for grafting of the roof-deficient acetabulum. Constrained or capture polyethylene liners are useful in the unstable hip.

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PubMed2006

[Computer-assisted positioning of the acetabular cup for total hip arthroplasty based on joint kinematics without prior imaging: preliminary results with computed tomographic assessment].

PURPOSE OF THE STUDY: Most navigation systems for computer-assisted total hip arthroplasty (THA) require prior computed tomography (CT) or acquisition of multiple bone landmarks on the pelvis. In order to avoid these problems, we developed a computer-assisted navigation system without CT based on a kinematic approach to the hip joint. The principle is to orient the cup in relation to the cone describing the hip joint range of motion. The purpose of this work was to analyze preliminary results. MATERIAL AND METHODS: Eighteen primary THA were implanted with the system (16 women, two men, mean age 68 +/- 7.8 years, age range 54-83 years, 18 degenerative hip disease). Two optoelectronic captors were fixed percutaneously on the pelvis and the distal femur. The acetabulum was prepared first followed by the femur using reamers and broaches of increasing size. The last broach placed in the femur was equipped with a large head adapted to the newly prepared acetabulum. The range of hip motion was recorded to determine the maximal range of motion cone. The acetabular cup was thus positioned in order the prosthesis range of motion included entirely the maximal range of motion of the hip joint. RESULTS: One patient fell three weeks after implantation causing posterior dislocation; there was no recurrence. The Postel-Merle-d'Aubligné score improved from 8 +/- 2.9 (range 3-12) preoperatively to 17 +/- 0.8 (range 16-18) at last follow-up. None of the patients complained about the captor insertion and there were no cases of hematoma or fracture. Operative time was 35-40 minutes longer for the first four cases and was progressively reduced 15-20 minutes for the last four cases. Mean leg length discrepancy was 5.6 +/- 7.5 mm (range 0-25) before implantation and 0.6 +/- 3 mm (range -5 to 10 mm) at last follow-up. CT-scan measurements revealed a mean anteversion of the femoral implant of 18.2 +/- 8.5 degrees (range 0-31). Anatomic anteversion of the cup (measured from the pelvis landmark and thus independently of the position of the pelvis) was 24.7 +/- 8.8 degrees (range 12-40). The sum of the femoral and anatomic acetabular anteversions was 43 +/- 13.1 degrees (range 22-71). Anteversions were 16 degrees for the cup and 16 degrees for the stem for the one case of dislocation. CONCLUSION: This method can be used in routine without lengthening operative time significantly. It safely controls leg length and helps position the cup. This study demonstrated that there is no ideal position for the cup which can be used for all patients. Because of the wide range of inclination and anteversion figures, half of the cases were outside the safety zone recommended by Lewinnek.

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PubMed1986

The impact of modern cement techniques on acetabular fixation in cemented total hip replacement.

A radiographic study was performed to assess acetabular fixation in 78 total hip replacements performed between 1971 and 1980. In 1979, the technique of acetabular component insertion was modified to include water-pik lavage, preservation of subchondral bone of the acetabulum during reaming, multiple fixation holes in the pubis ischium and ilium, and devices that improve pressurization of the cement into the cancellous bone surfaces. The impact of these techniques was studied. A cumulative radiolucency score was calculated for each acetabulum from 5-year follow-up radiographs, and the mean cup radiolucency scores for two chronologic groups were compared using the t-test for independent samples. No significant differences in patient age, weight, or sex, type of prosthesis, or approach used was found between groups. The acetabular components inserted between 1979 and 1980 had significantly lower cup radiolucency scores than those inserted between 1971 and 1978, at 5-year follow-up evaluation. Modern cement technique may be responsible for significantly enhanced durability of acetabular fixation in cemented total hip replacement.

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PubMed1997

Anatomic variation of structural properties of periacetabular bone as a function of age. A quantitative computed tomography study.

The shape of the acetabulum, the volume of the periacetabular bone, and its density for 125 patients with a wide age range have been quantified using quantitative computed tomography. The goals were to study the relationship between geometric and densitometric properties and provide normative data for finite-element analysis. Significant correlations were found between acetabular diameter and (1) depth, (2) cancellous periacetabular bone density, and (3) periacetabular total bone volume. Only changes in densitometric properties significantly correlated with age. Sphericity of the acetabulum did not increase with age. Variability in bone morphology and density was found for both male and female groups. Surgeons using purely geometric measures to quantify the integrity of acetabular bone should be aware of their limitations when selecting hardware for total hip arthroplasty.

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PubMed1997

Vastus-Psoas release for acetabular exposure in revision hip surgery.

A technique is presented for wide exposure of the acetabulum for revision total hip arthroplasty surgery in the presence of a solidly fixed, modular, or monoblock femoral component without the need for trochanteric osteotomy. The technique involves release of the proximal portion of the vastus lateralis, vastus intermedius, and vastus medialis muscles and the iliopsoas tendon form the femur and placement of the femoral head/neck posterior to the acetabulum. The exposure afforded by this release usually precludes the need for trochanteric osteotomy and/or removal of a well-fixed femoral component in revision surgery that is being done for isolated loosening of acetabular components, thereby decreasing operative time, morbidity, and the risks of complication of trochanteric osteotomy.

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PubMed1999

Acetabular fracture associated with cementless acetabular component insertion: a report of 13 cases.

Acetabular fracture during insertion of a cementless acetabular component occurred in 13 patients. The preoperative diagnosis was osteoarthritis in 6 patients, rheumatoid arthritis in 2 patients, avascular necrosis in 3 patients, hip fracture nonunion in 1 patient, and developmental dysplasia of the hip in 1 patient. Several different components were used; however, the acetabulum was underreamed by 1 to 3 mm in all cases. The acetabular fracture was identified in 9 of 13 cases intraoperatively. The fracture was identified on postoperative radiographs for the other 4 cases. Fractures were treated by a variety of means, including the addition of augmentation screws in or around the cup, use of autograft bone at the fracture site, modified postoperative weight-bearing status, and immobilization. In 2 cases, the socket needed to be revised after it progressively migrated and failed. One patient had cup migration, and another had a radiolucent line about the cup but was not symptomatic enough to require revision. In 3 of these 4 cases, the fracture was not identified intraoperatively. Underreaming of the acetabulum and use of an oversized acetabular component has been recommended to improve the initial stability of the acetabular component during total hip arthroplasty. Impaction of an oversized component requires bone to undergo plastic deformation if the cup is to be fully seated. Theoretically, this technique provides improved component stability with enhanced osseous ingrowth into the cup. The 13 cases reported in this study demonstrate that acetabular fracture is a complication that may occur in association with uncemented hip arthroplasty, particularly if oversized components are used. The importance of recognizing acetabular fractures intraoperatively and the need to institute appropriate treatment to ensure a stable acetabular component is emphasized. In patients with osteoporotic bone, line-to-line reaming with use of a cementless acetabular component or insertion of a cemented socket may be considered to avoid this significant complication.

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PubMed1997

Application of numerical modelling of osteotomy to orthopaedic practice.

During the development of an osteoarthritic hip joint, osteophytes, cysts as well as arthrosis originate on the contact boundary between the femoral head and the acetabulum in highly loaded human joints. The purpose of proximal femur osteotomy is to bring the femoral head into a new position inside the acetabulum. The corrective options of intertrochanteric osteotomy most frequently used in orthopaedic practice are valgization, varization, displacements, oblique displacements, lateralization, extension, rotation or shortening of the shaft. The present widespread tomographic measurement methods, such as computer tomography (CT), magnetic resonance imaging (MRI) and 2D or 3D reconstruction involve the simulation of surgical problems of osteotomy, as well as the simulation of the reconstruction of the function of the hip joint after the operation. The results of numerical modelling of osteotomy concerning contact problems, will be presented in the contribution.

Acetabulum↗
PubMedDate not supplied

Cartilage and labrum degeneration in the dysplastic hip generally originates in the anterosuperior weight-bearing area: an arthroscopic observation.

To clarify the intra-articular pathology of dysplastic osteoarthritis, we conducted 120 hip arthroscopies. Hips were classified radiologically into four stages: 41 prearthritic stage, 42 early-stage, 34 advanced-stage, and 3 end-stage. As the radiological stage progressed, articular cartilage degeneration became more extensive and severe. In the prearthritic and early stages, cartilage degeneration generally originated in the anterosuperior portion of the weight-bearing area of the femoral head and acetabulum. Cartilage degeneration of the acetabulum usually preceded that of the femoral head. Most detaching tears of the acetabular labrum originated in the anterosuperior area, too. In conclusion, cartilage and labrum degeneration in the dysplastic hip generally originates in the anterosuperior portion of weight-bearing area.

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PubMedDate not supplied

Biomechanical comparison of two plating techniques for fixation of acetabular osteotomies in dogs.

OBJECTIVE: To compare the failure properties of a 5-hole, 2.7-mm curved acetabular plate (AP) to a 5-hole, 3.5-mm reconstruction plate (RP) when applied to acetabular osteotomies. STUDY DESIGN: Cadaver study. ANIMALS OR SAMPLE POPULATION: Pelves of 8 mature, large-breed dogs. METHODS: A 5-hole, 2.7-mm AP and a 5-hole, 3.5-mm RP were contoured and applied to the dorsal acetabulum of each pelvis. A central acetabular fracture was simulated after plate application by a transverse osteotomy with a fine saw. Each acetabulum was loaded in a weight-bearing direction. A load-deformation curve was produced for each construct, and biomechanical properties of the AP and RP were compared with the Student's paired t-test. A P value of < .05 was considered significant. RESULTS: For the AP and RP composite respectively, the mean +/- SD maximum load to failure was 2,721 +/- 632 N and 2,488 +/- 800 N, the stiffness was 4.8 +/- 1.8 N/m and 5.3 +/- 1.9 N/m, and the energy absorbed was 15.1 +/- 5.2 Nm and 16.3 +/- 8.3 Nm. None of these differences was statistically significant. CONCLUSIONS: Both fixation techniques provided comparable strength, stiffness, and energy absorbed under the loading conditions of this study. CLINICAL RELEVANCE: Because of the relative ease of application, the 2.7-mm curved AP may be the practical choice for acetabular fracture repair in large dogs.

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PubMedDate not supplied

The effect of plate luting on reduction accuracy and biomechanics of acetabular osteotomies stabilized with 2.7-mm reconstruction plates.

OBJECTIVE: To compare the accuracy of reduction and biomechanical characteristics of acetabular osteotomies repaired with luted and nonluted reconstruction plates. STUDY DESIGN: In vitro study. ANIMALS: Pelves removed from 12 adult greyhounds. METHODS: Acetabular osteotomies were created and repaired with a 6-hole, 2.7-mm reconstruction plates in 24 cadaver hemipelves. Ten hemipelves each were assigned to group I and group II. An impression cast of each acetabulum in group I was made before luting (preluting cast). Group I plates were then elevated, luted, and replaced. A second cast of each acetabulum in group I was then made (postluting cast). Step, gap, and total areas of articular osteotomy incongruence were determined from the casts. Group I (luted plate repairs) and group II (nonluted plate repairs) hemipelves were loaded ventral-to-dorsal using a materials-testing machine. Stiffness, yield load, and maximal load sustained were determined. RESULTS: Mean gap and total area of articular osteotomy incongruence for group I preluted plate repairs (7.1 mm(2) and 8.6 mm(2), respectively) were significantly greater than for group I postluted plate repairs (4.1 mm(2) and 5.1 mm(2), respectively). Mean stiffness and maximal load for group I (681 N/mm and 2,555 N, respectively) were significantly greater than for group II (360 N/mm and 1,730 N, respectively). Mean step area and mean load at yield values were not significantly different between groups. CONCLUSIONS: Luted plate repairs of osteotomized acetabulae result in improved reduction and are stiffer and stronger than nonluted plate repairs. CLINICAL SIGNIFICANCE: Plate luting may improve the accuracy of reduction of acetabular fractures where anatomic reduction is required. Plate luting may also increase the stiffness and strength of fracture repairs and arthrodeses.

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PubMed2000

Hip and femur trauma.

Fractures that involve the acetabulum and proximal femur are common. These injuries frequently occur due to high-energy trauma and may result in significant morbidity and long-standing disability, or high mortality when associated with other injuries, particularly to vascular structures. In this article, classifications pertinent to fractures of the acetabulum, hip dislocations, and fractures of the femoral neck, intertrochanteric region, and subtrochanteric region of the femur are discussed in detail with emphasis on their radiographic features.

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PubMedDate not supplied

[The German Society of Orthopedics and Traumatology classification of bone defects in total hip endoprostheses revision operations].

PROBLEM: In revision alloarthroplasty the need for bone allografts increased. The documentation of the defects is not done routinely. METHOD: For better documentation the German Society for Orthopedics and Traumatology (DGOT) developed a new and practical defect classification system. It was tested clinically in the last 6 years. RESULTS: In the acetabulum and femoral shaft seven defect types were distinguished and presented in figures. For the acetabulum: 1 cavitary holes, 2-4 unisegmental, 5 bisegmental, 6 trisegmental, 7 pelvic instability. For the femur: 1 intramedullary 2 trochanter 3 calcar 4 med. shaft 5 lat. shaft 6 part. diaphysis 7 total diaphysis. CONCLUSION: With this classification system we could better compared different reconstruction approaches in endoprosthetic surgery.

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