A finite element analysis of factors influencing total hip dislocation

A previously validated three-dimensional finite element model was used to study how several total hip component design and surgical placement variables contribute to resisting the propensity for posterior dislocation in the case of leg crossing in an erectly seated position. The computational formulation incorporated treatments of polyethylene material nonlinearity and large displacement sliding contact. The primary outcome measures were the peak intrinsic moment developed to resist dislocation, and the ranges of motion before neck on lip impingement and before frank dislocation. Modifications of the acetabular linear design (chamfer bevel angle, lip breadth, head center inset) involved trading off improved peak resisting moment for compromised range of motion and vice versa. Increases of head size led to substantial improvements in peak resisting moment, but if the head to neck diameter ratio was held constant, had almost no influence on the component range of motion. For the leg crossing event studied, increased component anteversion, and even more so increased tilt (less net abduction), achieved improvements in range of motion and in peak resisting moment, but these changes imply diminished resistance to anterior dislocation from extension and adduction motion inputs.     

Results of total hip arthroplasty for Crowe Type III developmental hip dysplasia

From 1969 through 1980, 90 hips in 82 patients had cemented total hip arthroplasty for Type III developmental hip dysplasia. Seventy hips were reviewed at an average of 16.6 years (range, 5-23 years) after operation. Aseptic loosening developed in 53% of acetabular cups and 40% of femoral stems. Despite attempts to place acetabular components in the anatomic center, 18 cups (25.7%) were placed outside that area. Using a measurement method to determine the true acetabular region and approximate femoral head center, final acetabular loosening strongly correlated with initial cup placement. Loosening occurred in 15 of 18 cups (83.3%) initially positioned outside of the true acetabular region compared with loosening in 22 of 52 cups (42.3%) initially positioned within the true acetabular region. Acetabular loosening also correlated with initial lateral displacement or initial superior displacement of the hip center from the approximate femoral head center. Initial cup placement medial to the approximate femoral head center was predictive of successful long term acetabular component fixation. The method of acetabular reconstruction did not affect eventual cup loosening. Placement of the hip arthroplasty center of rotation in or near the true acetabular region is recommended.     

Use of osteonics UHR hemiarthroplasty for fractures of the femoral neck

A clinical and radiographic study of bipolar hip arthroplasties was performed for fractures of the femoral neck. All patients were treated with the Osteonics UHR system. Clinical results were evaluated in 77 patients (77 hips) who were observed for an average of 4.8 years (range, 2-10 years). At the latest followup, 67 (87%) patients were rated as having a good or excellent outcome according to the Hospital for Special Surgery hip rating system. Clinical ratings in patients treated with cementless UHR were similar to or better than those of patients with cemented UHR. Hip dislocation occurred in only 3 (2.3%) patients, in whom the hip joint was reduced by a closed procedure without inducing disassembly of the prosthetic components. None of the patients had definitive acetabular erosion. The motion of the outer head was evaluated radiographically in 63 patients in weightbearing and non-weightbearing conditions, 3 to 108 months after surgery. The relative motion at the 2 sites of articulation of the outer head had stabilized by 3 months after surgery and subsequently remained unchanged. The authors' findings indicate that UHR hemiarthroplasty of the femoral head is a reliable treatment for fractures of the femoral neck.     

Tripolar hip replacement for recurrent prosthetic dislocation

An innovative treatment is described for unstable total hip arthroplasty that uses a large inside diameter acetabular cup and a bipolar femoral head sized to approximate the diameter of the normal hip. Eight consecutive patients with recurrent prosthetic dislocations were treated with this tripolar hip. Joint stability was achieved in all patients, who have an average of 4.2-years' followup (range, 2.6-6.3 years).     

Polyethylene wear after total hip arthroplasty: the effect of a modular femoral head with an extended flange-reinforced neck

The use of modular components in total hip arthroplasty has been thought to contribute to accelerated polyethylene wear. Specifically, a modular femoral head with a flange extension and a longer neck may cause increased wear. The purpose of the current study was to evaluate the effect of a flange extension on polyethylene wear. Ninety-one patients who had had a total of 100 primary total hip arthroplasties were evaluated after an intermediate duration of follow-up. All of the acetabular components consisted of a hemispherical titanium-alloy fiber-mesh porous-coated shell with a nonelevated modular polyethylene liner; they were inserted without cement and with use of supplemental screws through the dome after so-called line-to-line reaming. All of the femoral components consisted of a modular head with a diameter of twenty-eight millimeters and either a long neck (with a flange extension) or a short or medium neck (without a flange extension). The study group comprised sixty-two patients (sixty-six hips) who had had radiographic evaluation that was adequate to allow the valid measurement of polyethylene wear. Thirty-two hips were in men, and thirty-four were in women. The mean age of the patients was fifty-six years, the mean weight was seventy-three kilograms, and the mean duration of follow-up was 6.1 years (range, four to eight years). The rate of polyethylene wear in the eleven hips in which the femoral component had a flange extension was significantly greater than that in the fifty-five in which the femoral component did not have a flange extension (mean, 0.17 compared with 0.11 millimeter per year; p = 0.009). Multivariate analysis showed that the presence of a flange extension was associated with increased polyethylene wear to a greater degree (F = 2.86) than were all other variables that were measured, including a younger age (F = 1.72), a more vertical angle of the acetabular component (F = 0.49), a heavier weight (F = 0.14), male gender (F = 0.11), and a smaller initial thickness of the polyethylene (F = 0.02). These data support an association between the presence of a modular femoral head with a flange extension and an accelerated rate of polyethylene wear. The presumed mechanism is an increase in peripheral, or so-called rim, impingement of the flange-reinforced neck on the acetabulum due to a decrease in the ratio between the diameters of the femoral head and neck.     

Disease and nonbattle injury among United States soldiers deployed in Bosnia-Herzegovina during 1997: summary primary care statistics for Operation Joint Guard

Lesions of the acetabular labrum should be treated by correcting the causes. In a steep acetabulum where the femoral head brings the acetabular labrum under tension and traction, the acetabulum should be rotated by triple pelvic osteotomy to slightly over-corrected acetabular measurements. Severely diminished acetabular and femoral anteversion can also lead to tears and impingement of the labrum. Then rotation of the femoral neck and/or rotations of the acetabulum by triple osteotomy to 15-20 degrees of anteversion are indicated. Our triple osteotomy technique differs from that of others mainly in the ischial osteotomy. It is performed from the posterior approach between the sciatic notch next to the ischial spine and the obturator foramen and is directed 20-30 degrees anteriorly from the frontal (coronal) plane. The osteotomies therefore are placed close enough to the acetabulum to allow free rotation, but they do not interfere with the circulation of the acetabulum, and the ligaments between the sacrum and ischium are left in normal tension. Our normal values of the acetabular position were tested by correlating the measurements with the absence of pain. The optimum is reached with a CE angle and a VCA angle of 30-35 degrees, an angle of the weight-bearing zone of +5 to -5 degrees and a migration index of 10-15%. Overcorrections again caused pain and should be avoided. Diminished anteversion of femur and acetabulum towards 0 degree also caused pain and should be corrected by triple and femoral osteotomy to 15-20 degrees of anteversion. In earlier follow-ups of 216 hips 5-10 years postoperatively, 82.3% of the joints showed no change in the degree of osteoarthrosis. Survival rate curves regarding the absence of pain demonstrated that pain was experienced again when joints were corrected insufficiently or overcorrected, while in good corrections the joints were free of pain in about 75%.     

Survivorship analysis of cemented total hip arthroplasty acetabular components implanted with second-generation techniques

The clinical and radiographic results of primary cemented total hip arthroplasty performed by a single surgeon, with particular emphasis on the performance of acetabular components implanted with so-called second-generation cement techniques, were studied. Seventy hips with 48 metal-backed and 22 polyethylene acetabular components were followed for a mean of 9 years (range, 5-11.5 years). The clinical results were evaluated using a recognized hip score. The fixation status of the cemented acetabular component was evaluated using two methods of measuring radiolucent lines at 5 years and at the last evaluation. Acetabular component loosening was defined as a circumferential radiolucent line, component migration, or revision for loosening. This study was unable to confirm the findings of others that demonstrated higher failure rates with cemented metal-backed components when compared with all-polyethylene components. The survival of cemented acetabular components with 28-mm head femoral prostheses was worse than the survival of cemented acetabular components with 22-mm femoral heads in other published reports, despite advances in cement techniques. Because of the high rate of loosening of cemented 28-mm-inner-diameter acetabular components at 5 and 10 years, the authors no longer use these cemented components for acetabular reconstruction.     

Primary endoprosthetic replacement for acute femoral neck fractures. A review of 150 cases

A review of 150 consecutive endoprosthetic replacements for acute displaced femoral neck fractures was undertaken to investigate the following serious criticisms of the method. The first is excessive hospital mortality and morbidity, especially in comparison to internal fixation procedures retaining the femoral head. The second is pain, derived from the "unphysiologic" nature of placing a metal prosthesis against otherwise normal acetabular cartilage. In the first instance the procedure is condemned as too major an operative procedure, poorly tolerated by elderly patients. In the second, it is a poor procedure if it requires revision in a patient incapable of withstanding more than one operation. A detailed follow-up shows that the in-hospital mortality in patients averaging 79.8 years of age, was 4%, lower than published mortality for either hemiarthroplasty or internal fixation. Close postoperative monitoring, antibiotic and antiembolic prophylaxis (2.0% infection, 6% embolic complications), and rapid mobilization contributed significantly to the increased survival. Painful endoprostheses, the most frequent complication, occurred in 16.7% of the 125 patients available for follow up at an average of 21 months. The causes of pain were considered technical problems judging prosthetic neck length, head size, sinking and loosening. Dissolution of the medial femoral neck was associated with a narrow stem prosthesis in five of six of these failures. The above statistics suggest that primary endoprosthetic replacement for displaced femoral neck fractures carries with it neither the excessive mortality and morbidity nor the pain induced potential for early reoperations that have been suggested by the recent literature.     

The effects of graft rotation on attachment site separation distances in anterior cruciate ligament reconstruction

We created a model to see if twisting the graft in an anterior cruciate ligament reconstruction affected the distance separating the femoral and tibial attachments of the perimeter fibers of a patellar tendon graft. Graft bone plugs were simulated by two 12.5-mm diameter Delrin cylinders. Holes, 1 mm in diameter, were placed at the four corners of a centralized rectangle measuring 5 by 10 mm. Graft ligament fibers were represented by color-coded sutures passed through the holes in the modeled bone plugs. This graft model was fixed in tunnels reamed under arthroscopic guidance at the anterior cruciate ligament attachment sites of the femur and tibia in six fresh-frozen knee specimens. Spring gauges were used to measure indirectly the changes in distance of separation during knee flexion between the femoral and tibial attachments relative to a zero defined at 90 degrees of knee flexion. The tibial cylinder was rotated at 45 degrees increments from 90 degrees external to 180 degrees internal rotation relative to the femoral cylinder and measurements were repeated after each incremental rotation. External rotation resulted in a statistically significant higher mean separation distance (4.5 mm) for peripheral graft attachments than internal rotation (2.8 mm) (P = 0.05).     

Neuroimaging in the high-risk infant: relationship to outcome

PURPOSE OF THE STUDY: Dislocation following total hip arthroplasty (THA) continues to be a problem. An innovative treatment is described with the intermediate Bousquet's prosthesis. This study reported 13 cases and demonstrates its high reliability despite the origins of the dislocation. Recurrent dislocation following initial dislocation, occurs in between 25 to 60 per cent of the cases reported in the literature. The main cause is a malpositioned prosthetic component and especially a retroverted acetabulum. The other reasons for dislocation were: trochanteric non-union, bone or cement impingement, previous surgery, age and neurologic disorder. In every case the instability of the hip may be caused or increased by muscular insufficiency. Various methods are described to control recurrent dislocation: repositioning the component, posterior acetabular wall component, trochanteric advancement, retentive acetabular component, bracing. When the cause is clear and isolated, the rate of success may be 70-80 per cent. This study examines the results of a revision procedure with the intermediate Bousquet's prosthesis. MATERIAL AND METHODS: 13 recurrent dislocations were treated with the intermediate Bousquet's prosthesis. There were 10 women and 3 men with an average age at operation of 73 years. The main cause in 7 cases was an abductor insufficiency including 4 trochanteric non unions. The other causes were 6 component malpositions, 7 previous surgery, 1 impingement. The average delay between the first dislocation and revision was one year. The Bousquet's acetabular component is an steel cup covered with alumina, impacted without cement. The polyethylene component is free in the cup and retentive on the femoral head. The femoral positioning was not modified. RESULTS: The revision did not correct all of the causes of luxation, however we noted only one case of dislocation and no recurrent dislocations. DISCUSSION: At last follow-up, all recurrent dislocations were controlled. Nevertheless, there remained 7 abductor insufficiencies and 4 femoral malpositionings. In the literature the rate of success depends on the cause. The main difficulty is the treatment of joint laxity. Some authors propose trochanteric advancement, a larger head, a posterior wall acetabular component, retentive acetabular component. Success is not uniform. The Bousquet's acetabular component supports joint laxity and femoral malpositioning. This allows to keep the same original femoral component when the risk is too high for a cemented prosthesis or impossible for a non cemented prosthesis. CONCLUSION: This treatment of the recurrent dislocation is reliable with a short and simple operation.     

Relationship of femoral head and acetabular size to the prevalence of dislocation

Two clinical studies, one prospective randomized and one retrospective, were performed to evaluate the relationship of femoral head size and acetabular component outer diameter to the prevalence of dislocation of the modular total hip replacement. Between October 1995 and April 1996, 31 primary total hip arthroplasties in 30 patients were randomized to a femoral head diameter of 22 mm or 28 mm, for two groups of acetabular components of outer diameters of 56 mm or larger and 54 mm or smaller. Head size (22 mm) and acetabular component outer diameter (> or = 56 mm) were found to increase the risk of dislocation. From December 1984 to January 1994, 308 primary total hip arthroplasties were performed through a posterior approach by one surgeon using a modular 28 mm femoral head and one type of uncemented acetabular component. The rate of dislocation for acetabular components with an outer diameter of 62 mm or larger was increased significantly (five of 36 hips, 14%) compared with those with an outer diameter of 60 mm or smaller (11 of 272 hips, 4%).     

Confirmed abuse cases in public residential facilities for persons with mental retardation: a multi-state study

Our experience with 10 patients who suffered midshaft fractures of the femur and injuries to their ipsilateral hips has resulted in a treatment protocol that we believe can avoid unnecessary complications. The surgical protocol is a three-stage procedure based on (1) intramedullary nailing of the femur with interlocking for preserving the anatomic length and rotation of the femur; (2) treatment of the hip joint injury by means of open reduction and internal fixation of the acetabular fracture and/or reduction and fixation of the fractured femoral neck; and (3) repair of the extensor mechanism. Eight patients received this treatment and had fast recoveries. Union of the femoral fracture and full range of motion of the knee joint were observed within 3 months. In contrast, two patients who had received different surgical treatment had incomplete functional recoveries. This study offers a treatment protocol for ipsilateral disruption of the extensor mechanism, hip joint injury, and midshaft fracture of the femur in the multiply injured patient that can achieve full recovery with no complications. This relatively rare combination of injuries is definitely worthy of special attention.     

Thermal expansion modular femoral head extractor for revision total hip arthroplasty

Removal of a prosthetic modular femoral head is sometimes desirable during revision hip arthroplasty. A femoral head extractor was designed to heat and expand the prosthetic femoral head, apply a gentle distraction load, and remove the femoral head without injury to the femoral neck, taper, or bone-prosthesis interface. The device was used clinically in six hip revision cases. In five hips with cobalt-chrome heads and titanium alloy tapers, femoral heads were removed successfully; femoral fixation was maintained and femoral components were not visibly damaged. In the sixth case, the female portion of the taper junction was contained in a long femoral head sleeve. Heating the ball did not adequately expand the sleeve to allow easy ball removal.     

Unipolar versus bipolar hemiarthroplasty for the treatment of femoral neck fractures in the elderly

This paper presents the short term results of an ongoing prospective randomized trial comparing a cemented unipolar with a cemented bipolar hemiarthroplasty for the treatment of displaced femoral neck fractures in the elderly. Forty-seven patients with an average age of 77 years completed 6-month followup. Outcomes at 6 weeks, 3 months and 6 months were assessed by completion of a patient oriented hip outcome instrument and by functional tests of walking speed and endurance. No differences in the postoperative complication rates or lengths of hospitalization were seen between the two groups. Patients treated with a bipolar hemiarthroplasty had greater range of hip motion in rotation and abduction and had faster walking speeds. However, no differences in hip rating outcomes were found. These early results suggest that use of the less expensive unipolar prosthesis for hemiarthroplasty after femoral neck fracture may be justified in the elderly.     

Colchicine in chronic hepatitis B: a pilot study

INTRODUCTION: The authors report the case of an internal rotation of the lower limb, lately ascribed to a posterior placement of the acetabular component during total hip arthroplasty. MATERIAL AND METHOD: A 58 years old female had an irreducible internal rotation of the right hip 3 years after total hip arthroplasty for arthritis. When the hip was extended, the lower limb showed an irreducible internal rotation of 45 degrees. In flexion of the hip this rotation disappeared. AP radiograms showed femur and femoral stem in internal rotation, a healed fracture of the acetabulum, and the acetabular component seemed to be in correct position. On CT scan the acetabular component was 4 cm posterior to the anatomic location, although there was no abnormal anteversion of the stem and acetabular component. Revision, with relocation of the acetabular component, corrected lower limb rotation. DISCUSSION: Posterior position of the acetabular component has not been described as a cause of lower limb malrotation. Normally the strength of the external hip rotators muscles is three times as important as of the internal rotators. The transverse acetabular fracture led to backwards placement of the acetabular component and yelded in an automatic internal rotation of the femur, because the trochanter kept an anatomical position in the horizontal plane. The posteriorised rotation center of the hip had changed the balance of the different rotator muscles, some of them, originally external rotators, becoming internal rotators.     

Hip arthroplasty by matching cups

A total hip surface arthroplasty consisting of matching cups and uncemented prosthetic components is a noteworthy operation. The femoral cup obtains cylindrical support from the femoral head which is reamed in the shape of a cylinder. The acetabular cup is metallic with a polyethylene liner. It is mobile over the bone but its position is constrained by contact with the femoral cup and therefore "self-centering." On the femoral side, the cup must be placed strictly in the axis of the femoral neck. The main consideration in femoral head surface replacement is the vitality of the underlying bone. Necrosis was observed in the earliest clinical trials but there have been no cases of necrosis in the past 3 1/2 years. This is attributed to a more limited surgical approach in which only the anterior part of the gluteus medius is divided and all the posterior elements of the hip are preserved. The acetabulum is sufficiently reamed to receive the cup, which protrudes beyond the external margins of the acetabulum in all positions. Errors have been committed while perfecting the prosthetic material, but the results as determined by a 6 1/2 year follow-up on purely metallic cups are encouraging. Metal-polyethylene cups presently under investigation have almost a 2 year follow-up. The reaction of the acetabulum to an uncemented cup is not yet known. However, the existence of 2 sliding surfaces and the fact that the acetabular cup moves only during the extremes of hip movement, is reason to assume that if the acetabulum is not reamed to expose cancellous bone, the risks of protrusion are minimal or delayed. Total surface arthroplasty by concentric cups has been performed in 335 hips to date. The operation is especially recommended when osteotomy is no longer possible and disabling coxarthrosis is present in relatively young patients.     

Neck afferents and muscle sympathetic activity in humans: implications for the vestibulosympathetic reflex

We have shown previously that head-down neck flexion (HDNF) in humans elicits increases in muscle sympathetic nerve activity (MSNA). The purpose of this study was to determine the effect of neck muscle afferents on MSNA. We studied this question by measuring MSNA before and after head rotation that would activate neck muscle afferents but not the vestibular system (i.e., no stimulation of the otolith organs or semicircular canals). After a 3-min baseline period with the head in the normal erect position, subjects rotated their head to the side (approximately 90%) and maintained this position for 3 min. Head rotation was performed by the subjects in both the prone (n = 5) and sitting (n = 6) positions. Head rotation did not elicit changes in MSNA. Average MSNA, expressed as burst frequency and total activity, was 13 +/- 1 and 13 +/- 1 bursts/min and 146 +/-34 and 132 +/- 27 units/min during baseline and head rotation, respectively. There were no significant changes in calf blood flow (2.6 +/- 0.3 to 2.5 +/- 0.3 ml.100 ml-1.min-1, n = 8) and calf vascular resistance (39 +/- 4 to 41 +/- 4 units; n = 8). Heart rate (64 +/- 3 to 66 +/- 3 beats/min; P = 0.058) and mean arterial pressure (90 +/- 3 to 93 +/- 3; P < 0.05) increased slightly during head rotation. Additional neck flexion studies were performed with subjects lying on their side (n = 5), MSNA, heart rate, and mean arterial pressure were unchanged during this maneuver, which also does not engage the vestibular system. HDNF was tested in 9 of the 13 subjects. MSNA was significantly increased by 79 +/- 12% (P < 0.001) during HDNF. These findings indicate that neck afferents activated by horizontal neck rotation or flexion in the absence of significant force development do not elicit changes in MSNA. These findings support the concept that HDNF increases MSNA by the activation of the vestibular system.     

Observations on the direction of wear in Charnley sockets retrieved at revision

The direction of wear in the acetabular socket has implications for the amount of debris that is generated during movement, for the magnitude of eccentric loading and for the incidence of impingement of the neck. We observed the direction of penetration with respect to a global co-ordinate system in 84 acetabular components retrieved at reoperation. The mean direction of wear relative to the open face of the sockets was found to be 37 degrees with a range from 0 degrees to 87 degrees. For those values determined using the inclination of the socket on the prerevision radiograph, the mean direction of penetration in the coronal plane had a lateral, rather than a medial, component. The mean angle was 84 degrees (SD 17 degrees) with respect to the horizontal. The angle of penetration was found to correlate significantly with the depth, in that the lateral component became larger as the wear progressed. There was also a significant correlation between the rate of penetration and the direction of wear. Despite the theoretical advantage of penetration in the superolateral direction, i.e., along the margin of the socket, in reducing the probability of impingement of the neck, no significant correlation was seen between the angle of penetration and the period of use in vivo. This may suggest that impingement of the femoral neck on the rim of the socket may not be the dominant factor in loosening of the socket but can still be important in a few cases.     

How to evaluate suspected immunodeficiency

The periacetabular osteotomy is a strategy for the treatment of residual hip dysplasia in young adults with the aim of preventing secondary coxarthrosis. This polygonal, juxta-articular osteotomy respects the vascular blood supply to the acetabular fragment and thus facilitates an extensive acetabular reorientation with improvement of the insufficient coverage of the femoral head, including medial displacement of the fragment. All osteotomies are performed by one approach, the modified Smith-Petersen, which allows an anterior capsulotomy. Inspection of the joint not only provides information on acetabular rim pathologies, but also facilitates the control of impingement-free range of motion after the correction. The posterior column remains partially intact, allowing minimal internal fixation of the acetabular fragment and early mobilization similar to that after an intertrochanteric osteotomy. The dimensions of the true pelvis are unchanged, providing the capacity to have an unimpeded delivery in women. This paper describes the preoperative evaluation, current indications, surgical technique, postoperative care, and the results of this osteotomy.     

Flexion space configuration in total knee arthroplasty

Equal resection of the posterior femoral condyles combined with a 90 degree tibial resection results in a trapezoidal flexion space. Two groups of patients were studied; in one group, the flexion space was allowed to remain trapezoidal, whereas in the other group, the anteroposterior femoral resections were externally rotated to allow rectangularization of the flexion space. In the second group, the range of flexion was increased and the incidence of medial tibial pain and zone I radiolucencies decreased. Other than for knees in a hypervalgus position before surgery, the mean amount of rotation required was 3 degrees +/- 0.2 degrees.