Judy R. Feinberg

Morphologic features of the acetabulum and femur: Anteversion angle and implant positioning

Morphologic features of the hips, in particular those features germane to determination of acetabular and femoral anteversion angles and femoral head offset, were studied in 50 male and 50 female human skeletons with bilateral normal joints. Four distinct configurations were identified relative to the anterior acetabular ridge. The majority (121, 60.5%) were curved; 51 (25.5%) were angular; 19 (9.5%) were irregular; and nine (4.5%) were straight. The acetabular anteversion angle measured 19.9° ± 6.6° (range, 7°–42°) and was significantly larger in females (21.3° ± 7.1°) versus males (18.5° ± 5.8°). The notch acetabular angle, which can be identified easily intraoperatively, was defined as the angle created at the intersection of a line from the sciatic notch along the posterior acetabular ridge and a line from the posterior to the anterior acetabular wall. This angle is almost perpendicular (89.0° ± 3.5°) and, therefore, may provide an accurate estimate of acetabular anteversion during cup placement. Awareness of the anatomic differences between genders for acetabular anteversion angle, anterolateral bowing of the femur, and neck shaft angle may help reduce the relatively higher incidence of dislocation in females and may lead to different implant designs for male and female patients.

Hydroxyapatite-Coated Total Hip Femoral Components in Patients Less Than Fifty Years Old. Clinical and Radiographic Results after Five to Eight Years of Follow-up*

One hundred and thirty-three patients (152 hips) who were an average of thirty-nine years old (range, sixteen to forty-nine years old) received a proximally hydroxyapatite-coated femoral prosthesis as part of a total hip arthroplasty and were followed for a minimum of five years (average, 6.4 years; range, five to 8.3 years) or until revision. The average Harris hip score was 47 points (range, 22 to 77 points) preoperatively and 93 points (range, 49 to 100 points) at the time of the latest clinical evaluation. Two patients who had a well fixed femoral implant had activity-limiting pain in the thigh at the time of the most recent examination. Radiographic changes consistent with bone-remodeling (cortical hypertrophy and bone condensation) typically were seen around the mid-part of the shaft of the prosthesis. Forty-eight (32 per cent) of the 148 hips that were included in the radiographic analysis demonstrated a small amount of erosive scalloping in either zone 1 or zone 7 of Gruen et al., and intramedullary osteolysis was suspected in only one hip. All stems were radiographically osseointegrated according to a modification of the criteria described by Engh et al. Four stems were revised, but none of the revisions were performed because of mechanical failure (two stems were revised in conjunction with a revision of the cup because of pain; one, because of an infection; and one, after a traumatic femoral fracture that occurred six years postoperatively). Thus, the rates of aseptic and mechanical failure were both 0 per cent. The combined rate of failure, which included the two stems that were revised because of pain and the two stems that were associated with pain that limited activity, was 2.6 per cent (four of 152 stems). The over-all clinical results associated with hydroxyapatite-coated femoral components were excellent in this group of young patients after intermediate-term follow-up. A review of serial radiographs showed mechanically stable implants with osseous ingrowth, evidence of stress transmission at the middle part of the stem, and minimum endosteal osteolysis.

Hydroxyapatite coated implants. Total hip arthroplasty in the young patient and patients with avascular necrosis.

Two high risk groups for total hip arthroplasty, 136 patients (155 hips) younger than 50 years of age (average age, 38 years) and 44 patients (53 hips) with the diagnosis of avascular necrosis, have a minimum followup of 5 years and a mean followup of 6.8 years. The average Harris Hip Score at last followup totaled 93 and 90, respectively, and thigh pain was reported in 1.3% and 3.8%, respectively. All patients in both groups received the same hydroxyapatite coated femoral stem and the mechanical failure was 0%. No stem was revised for aseptic loosening, 100% of stems were bony stable by radiographic criteria, new bone formation was progressive about the femoral stem, and 0% endosteal lysis was found. The acetabular components had a mechanical failure rate of 10% and 7.5%, respectively, without osteolysis, and an additional 7% and 7.5% failure as a direct result of progressive osteolysis. The results with the porous press fit and hydroxyapatite threaded sockets were far superior to that of the smooth hydroxyapatite press fit sockets and socket failure was associated with thin polyethylene liners and the use of 32-mm head diameters. These findings show a high success rate with a nonporous hydroxyapatite coated titanium femoral stem. However, hydroxyapatite on a smooth acetabular component yielded less predictable results indicating that for long term fixation of the acetabulum an interlock of bone is preferred.

Omnifit cementless total hip arthroplasty: A 10-year average followup

Seventy-six hips in 67 patients were evaluated an average of 119 months (range, 61-150 months) after total hip arthroplasty with porous coated Omnifit femoral and acetabular components. The patients were young (average age, 45 years), and most were male (67%). Two stems and one cup were revised for aseptic loosening, for aseptic revision rates of 2.6% on the femoral side and 1.3% on the acetabular side. Thigh pain was present in three cases, one of which was activity limiting. Twenty-five (35.7%) hips had evidence of osteolysis confined to proximal Gruen Zone 1 or 7 or to the acetabulum (22 proximal femoral, three both). There were no cases of intramedullary osteolysis in surviving stems. Thirteen (17.1%) hips have undergone reoperation for bone grafting of progressive proximal osteolysis without component revision, at an average 93 months after the total hip arthroplasty. At an average 40 months after reoperation, all stems remain well fixed, and there has been no recurrence of osteolysis of grafted femoral lesions. These results suggest that a circumferentially proximally porous coated femoral component in cementless total hip arthroplasty can provide stable fixation for as long as 12 years after implantation and caseal the canal from distal osteolysis. Serious concerns remain about the incidence of proximal femoral osteolysis.

Interobserver variability of gait analysis in patients with cerebral palsy.

In this study 11 ambulatory patients (mean 10.8 years) with spastic cerebral palsy were each evaluated with instrumented gait analysis at four different centers. After review of the data, each medical director chose from a list of treatment options. The average variability in static range of motion from physical examination ranged from 25° to 50°. Hip and knee sagittal motion had the best relative variability of 20° to 24%. Via gait analysis, the average variability in sagittal, coronal, and transverse plane kinematic motions averaged 12,° 7°, and 20°, respectively. Increased variability was noted in transverse (worst) to coronal and finally sagittal (best) plane motion. Only two mildly affected patients had similar, but not exact, treatment recommendations. The authors conclude that substantial variations in raw data exist when the same cerebral palsy patient is evaluated at different gait centers. These data do not yield the same treatment recommendations in the majority of patients.

Hydroxyapatite-coated femoral components: 15-year minimum followup.

Hydroxyapatite-coated femoral components were introduced to enhance fixation, but concerns were raised about whether the coating would be maintained over time. We therefore determined the long-term clinical and radiographic results of a proximally hydroxyapatite-coated femoral component and compared the mechanical failure rate to other fixation methods at similar lengths of followup. The study group, culled from a large, multicenter prospective study population, consisted of 146 patients (166 hips) with followup of 15 to 18 years. Average age at time of the index procedure was 51 years, and the most common diagnoses were osteoarthritis (71%) and osteonecrosis (11%). Average Harris hip scores were 42.7 preoperatively and 91.5 at most recent followup. Radiographically, one stem showed stable fibrous fixation, and all other unrevised stems were bony stable. Of 13 stem revisions in the study population, only one stem has been revised for aseptic loosening. Forty-nine percent of hips have an osteolytic lesion in proximal areas of Gruen Zones 1, 7, 8, or 14 only. Both the femoral aseptic revision and mechanical failure rates are 0.6% at 15-year minimum followup. The data demonstrate excellent long-term survivorship of this hydroxyapatite-coated femoral component used in a relatively young patient group.Level of Evidence: Level IV, therapeutic study. See the Guidelines for Authors for a complete description of levels of evidence.

Factors related to false- versus true-positive neuromonitoring changes in adolescent idiopathic scoliosis surgery

Study Design. A retrospective study of 134 adolescent patients who underwent surgical correction of idiopathic scoliosis between June 1992 and August 1998 was conducted. Objective. To examine factors related to changes in somatosensory-evoked potentials with or without neurogenic motor-evoked potentials. Summary of Background Data. Studies document and demonstrate threshold criteria for changes in neuromonitoring that predict changes in spinal cord function. Rates of false-negative occurrences are low, yet higher rates of false-positive findings may result. Methods. All the patients had somatosensory monitoring, and 71 patients had both somatosensory-evoked potential and neurogenic motor-evoked potential monitoring. Gender, age, curve types, duration of surgery, type and amount of instrumentation, and amount of correction were examined for their effects on monitoring. Estimated blood volume loss as well as high and low mean arterial pressure and its variance were assessed at the start, middle, and conclusion of the procedure. Results. According to the findings, 122 patients (91%) had no monitoring changes and no postoperative neurologic deficit. Six patients (4.5%) had false-positive readings. Six patients had a postoperative motor or sensory deficit, all of which resolved within 18 months. False-positive readings were associated with greater variability in mean arterial pressure. No consistent predictions could be made about the incidence of cord injury if neuromonitoring changes returned to baseline before the end of surgery. Conclusions. Questions remain about the predictive accuracy of somatosensory-evoked and neurogenic motor-evoked potentials. According to the findings in this study, in which there were no false-negative readings and a modest false-positive rate, continued use of these methods is recommended. Higher false-positive rates were seen in patients with greater lability in mean arterial pressure. A wake-up test is recommended for all cases in which threshold monitoring changes occur because cases of spinal cord injury may exist even when monitored variables return to baseline.

Varus derotation osteotomy for the treatment of hip subluxation and dislocation in cerebral palsy: statistical analysis in 73 hips.

The purpose of this study is to review the results of varus osteotomy in patients with cerebral palsy and to determine factors that influence the rates of residual hip displacement. A retrospective chart review of 65 patients who underwent 79 varus osteotomies was performed. Preoperative, postoperative and follow-up radiographs were analyzed for routine radiographic measurements, pelvic obliquity, osteonecrosis (avascular necrosis), joint incongruity or degenerative joint disease. The average follow-up was 5.2 years (range, 1.1-18.4 years). At follow-up, 3 hips were dislocated, 19 were subluxated and 57 were stable (72%). Age at surgery and the degree of preoperative hip displacement had significant effects on outcome. The average age at surgery for initially subluxated hips, which were located at follow-up, was 7.2 years. This was significantly younger (P = 0.008) than initially subluxated hips, which were displaced (10 years of age). Subluxated hips at surgery were also more likely to be located at follow-up than dislocated hips.

Evaluation of the Forearm in Untreated Adult Subjects with Multiple Hereditary Osteochondromatosis

Background: Limb-length discrepancy or angular deformities as a result of altered bone growth may lead to a decreased range of motion and impaired function as well as premature osteoarthritis in patients with multiple hereditary osteochondromatosis. The purpose of this study was to describe the function of the forearm in untreated patients in order to facilitate comparison with studies of the results of treatment of this condition.Methods: The medical records of fifty-one pediatric patients were identified and served as the basis for identifying a cohort of adult relatives with the disorder. Participants were asked about pain and limitations in vocational or recreational activities and about concerns with regard to cosmetic appearance. Radiographs of the forearm and wrist were made to quantify the deformity. Functional outcome was assessed on the basis of a comparison with the norms for grip and pinch strength and for scores on the hand function test of Jebsen et al. Limitations in the range of motion of the upper extremities were converted to standard impairment ratings.Results: Participants included twenty-two men and seventeen women with an average age of forty-two years (range, twenty to eighty years). Most of the patients were employed in careers of their choice, with only five (13%) indicating that they were limited in any way in the performance of their jobs. Twenty-six subjects (67%) participated in recreational activities, and sixty-eight arms (88%) were reported to be free of pain. Objective measurement of function demonstrated greater disability than that found from subjective reporting. Fourteen arms had an impairment rating of >10%, while twenty had decreased pinch strength and sixteen had decreased grip strength. Ten arms (13%) had decreased hand function according to the hand test of Jebsen et al. Radiographic evaluation demonstrated osteoarthritic changes in three limbs.Conclusions: Affected individuals had definite decreases in hand and wrist function, yet these did not result in major increases in pain or in limitations in daily work and recreation. This cohort provides a basis for comparison with the results of operative treatment in affected individuals with multiple hereditary osteochondromatosis.

Orthopaedic implants in children: survey results regarding routine removal by the pediatric and nonpediatric specialists.

Abstract: The role of orthopaedic implant removal in children is controversial. Some children later require adult reconstruction; implant removal may be difficult or may adversely affect the outcome. The purpose of this study is to compare the opinions of the pediatric and nonpediatric specialists regarding routine implant removal in children. Participants were asked to complete a Web-based questionnaire containing demographics, general opinions, and a series of specific case scenarios related to implant removal/retention. The study group consisted of 273 pediatric, and 99 nonpediatric specialists, with an average of 17-year experience. Regarding asymptomatic, stainless steel implants in children, 41% indicated removal most or all of the time, 36% reported sometimes, and the remaining 22% reported almost never or never. Implant location was the only important factor in the decision to remove or retain the implant. A greater percentage of pediatric specialists endorsed implant retention in the hip or pelvis in older children compared with nonpediatric specialists. More experienced surgeons, regardless of specialty area, recommended implant removal. Pediatric specialists may wish to reconsider their preference to retain large hip implants in older children because their nonpediatric colleagues, who presumably are faced with the removal from these children when they reach adulthood, recommend implant removal once they have served their purpose. The number of such cases and the role of early removal in improving the long-term outcome need further study.