Posterior compact Cotrel-Dubousset instrumentation for occipitocervical, cervical and cervicothoracic fusion.

The authors report on 32 consecutive patients with instability at the craniocervical, cervical and cervicothoracic regions suffering from various pathologies, who were treated with posterior instrumentation and fusion using the posterior hooks-rods-plate cervical compact Cotrel-Dubousset (CCD) instrumentation alone or, in three patients, in combination with anterior operation. The patients were observed postoperatively for an average of 31 months (range 25-44 months) and evaluated both clinically and radiographically using the following parameters: spine anatomy and reconstruction, sagittal profile, neurologic status, functional level, complications and status of arthrodesis. All patients but one (who died) achieved a solid arthrodesis based on plain and flexion/extension roentgenograms. Cervical lordosis (skull-C7) and cervicothoracic kyphosis (C7-T2) was improved by instrumentation towards a physiological lateral curve by an average of 33% (P<0.05) and 28% (P<0.05) respectively. Anterior vertebral olisthesis was reduced in the craniocervical and cervicothoracic region, by 73% and 90% respectively. At final follow-up there was an improvement of the neurologic Frankel status by an average of 1.2 grades and of myelopathy in 75% of the operated patients. Good to excellent functional results were seen in 77% of the operated patients, while acute and chronic pain was reduced by an average of 2.4 grades, on a scale of 0-3, in operated patients. No neurovascular or pulmonary complications arose from surgery. There was no significant change in lateral spine profile and olisthesis at the latest follow-up evaluation. There were no instrument-related failures. One patient requested hardware removal in the hope of reducing postoperative pain in the cervicothoracic region. The poor and fair results were related to the lack of improvement of neurologic impairment and myelopathy. The results of this study demonstrate that cervical CCD instrumentation applied in the region of the skull to the upper thoracic region for various disorders is a simple and safe instrumentation that restores lateral spine alignment, improves the potential for a solid fusion and offers sufficient functional results in the vast majority of the operated patients. However, the use of hooks in spinal stenosis is contraindicated.

Treatment of dysplastic and congenitally dislocated hips with the Zweymueller total hip prosthesis.

Uncemented Zweymueller total hip prostheses were implanted in 35 dysplastic or dislocated hips in 33 patients. Sixteen hips were dislocated and 19 hips were dysplastic; in 12 hips, an intertrochanteric or pelvic osteotomy was performed in early childhood. In all cases, the titanium screw socket was implanted at the level of the original cotyloid cavity. Osteotomy of the greater trochanter, shortening osteotomy, or roof acetabuloplasty were not performed. In cases in which the femoral cavity was too narrow for the Zweymueller stem, an anterolateral longitudinal window-shaped osteotomy was performed. In cases of severe dysplasia, cotyloid cavity bone grafts from the resected femoral head were placed medially to reinforce the acetabular bottom. Clinical and radiographic follow-up ranged from 3-8 years. Average Harris hip score improved from 47 points preoperatively to 86.2 points postoperatively. Complications included two primary anterior dislocations, two temporary femoral nerve pareses, and two deep vein thromboses. At longest follow-up evaluation, no revision was indicated in any of the hips. Satisfactory results in this series were attributed to careful patient selection, precise preoperative radiographic planning, and an operative technique that included implantation of the socket at the primary acetabulum and achievement of primary stability using press-fit fixation.

Effectiveness of transfixation and length of instrumentation on titanium and stainless steel transpedicular spine implants.

This study compares the effectiveness of transfixation on the stiffness of two pedicle screw-rod constructs of different manufacture, implant design, and alloy, applied in one-and two-level instability. Four screws composed of either stainless steel or Titanium were assembled in pairs to two polymethylmethacrylate blocks to resemble one-and two-level corpectomy models and the construct underwent nondestructive torsional, extension, and flexion loading. In every loading test, each construct was tested using stainless steel or titanium rods of 4.9-mm diameter in two different lengths (short, 10 cm; long, 15 cm), not augmented or augmented with different transfixation devices or a pair of devices. The authors compared the stiffness of stainless steel and titanium constructs without cross-link with the stiffness of that reinforced with single or double Texas Scottish Rite Hospital (TSRH) cross-link, closed new-type cross-link (closed NTC), or open new-type cross-link (open NTC). The results showed that augmentation or no augmentation of short rods conferred significantly more stiffness than that of long rods of the same material in all three loading modes. The closed NTC provided the greatest increase of torsional, extension, and flexion stiffness, and single TSRH provided the least amount of stiffness. Torsional stiffness of short stainless steel rods augmented or not augmented was significantly greater than that of their titanium counterparts. Torsional stiffness of long titanium rods was always greater than that of their stainless steel counterparts. Extension stiffness of short nonaugmented titanium rods was superior to that of long titanium rods, whereas extension stiffness of nonaugmented short and long stainless steel rods was similar. Nonaugmented short titanium rods showed greater flexion stiffness than that of long titanium rods. Long stainless steel rods displayed significantly greater flexion stiffness than did their titanium counterparts. This nondestructive study showed that cross-links increase the torsional stiffness significantly but less so the flexion and extension stiffness of both titanium and stainless steel posterior transpedicular constructs. This increase was proportional to the cross-sectional diameter of the cross-link. Titanium constructs showed more torsional stiffness when used in two-level instability and steel showed more torsional stiffness in one-level instability, particularly when they are reinforced. Stainless steel constructs showed greater flexion stiffness when they were used in two-level and titanium showed greater flexion stiffness in one-level instability, particularly when they were reinforced with stiff cross-links. The effect of transfixation on extension forces was obvious when thick cross-links were used.

Prediction of thoracic kyphosis using the Debrunner kyphometer.

The Debrunner kyphometer is an accepted tool for detecting and evaluating thoracic kyphosis. This prospective study was conducted to create a mathematical formula that provides, with high approximation, the roentgenographic angle of thoracic kyphosis (T4-T12) using only the kyphometer. Several clinical (kyphometer value, age, and sex) and radiographic (Cobb angle [T4-T12]) parameters from 90 consecutively screened adolescents (44 male and 46 female) were correlated using simple and multiple linear regression analyses. The reliability of measurement using the Debrunner kyphometer was high. The kyphometer value was strongly correlated with the roentgenographically measured thoracic Cobb angle (simple linear regression analysis; probability range, 0.0026 to 0.0002). There was no correlation between age or sex and thoracic kyphosis. The predicted kyphosis angle using the kyphometer and the mathematic formula was 44.66 degrees +/- 2.68 degrees, (range 27 to 62 degrees), and the real roentgenographic kyphosis angle was 47.5 degrees +/- 3.53 degrees, (range, 24 to 70 degrees). The kyphometer and formula were more reliable and accurate when kyphosis less than 50 degrees was measured. In this study, the authors constructed a mathematical formula that accurately provides the roentgenographic T4-T12 kyphosis angle in adolescents using only the Debrunner kyphometer with a deviation of less than 3 degrees. The authors recommend that all physicians engaged in kyphosis screening programs use the kyphometer combined with the recently constructed simple mathematic formula. This method will reduce the cost of school screening programs, overdiagnoses, and unnecessary exposure of adolescents to irradiation.

Medium- and long-term results of open reduction and internal fixation for unstable pelvic ring fractures.

Over a 10-year period, 74 patients with unstable pelvic injuries were treated with open reduction and internal fixation. Radiographic and clinical follow-up averaged 71 months (range: 38-141 months). Satisfactory (ie, good and very good) radiographic results were obtained in 90% of patients. Clinical results were superior in patients without associated injuries (P=.05-.001). Most of the complications in this series were due to associated injuries. Sepsis was mostly due to open pelvic injuries and malunion to either lack of patient cooperation or inadequate open reduction and internal fixation. Careful preoperative analysis of the nature of the pelvic injury and selection of the appropriate operative technique for open reduction and internal fixation result in a satisfactory outcome for the majority of operative patients.

Posterior stabilization of unstable sacroiliac injuries with the Texas Scottish Rite Hospital spinal instrumentation.

This article describes a new alternative technique for stabilization of unstable sacroiliac injuries using the Texas Scottish Rite Hospital (TSRH) instrumentation. The TSRH instrumentation was applied in 14 consecutive patients with unstable posterior pelvic ring disruptions. All patients underwent follow-up for an average of 29 months. Clinical results, using the rating system of d'Aubigne, were good in 9 and satisfactory in 5 patients. No pressure sores, infection, significant loss of correction, or hardware failures were observed postoperatively. The use of the TSRH instrumentation for stabilization of sacroiliac injuries offered sufficient stabilization of the posterior pelvic ring and permitted early mobilization without loss of correction.

Correlative analysis of the sagittal profile of the spine in patients with beta-thalassemia and in healthy persons.

This prospective study compares several roentgenographic parameters of the thoracic and lumbar spine in patients with beta-thalassemia and in healthy persons who served as controls. Eighty-four patients with beta-thalassemia and 84 age- and gender-matched healthy persons were examined clinically and radiologically (thoracic kyphosis, lumbar lordosis, and vertebral and sacral inclination). Although there was a significant difference in the vertebral inclination from T6 to L1, L4, and L5 between patients and controls, thoracic kyphosis and lumbar lordosis did not differ in the two groups. The apical vertebra of the thoracic kyphosis in patients and controls was T7 and T6, respectively, whereas L4 was the apical vertebra of the lumbar lordosis in both groups. There were no age- or gender-related differences in the magnitude of sacral inclination, thoracic kyphosis, or lumbar lordosis in the patients with beta-thalassemia compared with controls. Lumbar lordosis was significantly correlated with sacral inclination in both patients with beta-thalassemia and controls. Beta-thalassemia does not affect sagittal profile of the thoracic and lumbar spine but it is associated by structural changes on the frontal plane of the spine that are expressed as a high prevalence of scoliosis.

Factor analysis of the effectiveness of transfixation and rod characteristics on the TSRH screw-rod instrumentation.

The effects of Texas Scottish Rite Hospital (TSRH) hardware parameters (rod length and diameter and cross-link) and their interaction on the stiffness of the TSRH pedicle screw-rod construct were evaluated. Four TSRH screws were assembled in pairs to two polymethyl-methacrylate blocks to resemble a one-level or more corpectomy model and the construct underwent nondestructive torsional, extension, and flexion loading. In every loading test, each construct was tested using TSRH rods of different lengths (10, 15, and 20 cm) and diameters (4.9 and 6.5 mm) and different cross-links (TSRH and two new types made for this experiment). We compared the stiffness of the construct without cross-linking with that with single or double TSRH cross-linking, or either the closed new-type cross-link (closed NTC) or the open new-type cross-link (open NTC) using factor analysis. There was no axial slipping of one rod versus the other up to a force of 100 kg. The stiffness of the construct in all three loading modes increased as the rod length decreased, the rod diameter increased, and the construct was augmented with a cross-link. The closed NTC provided the greatest stiffness and the single TSRH provided the least stiffness. Unaugmented 10-cm-long rods showed two or three times more torsional stiffness than did that of the longer unaugmented rods independent of rod diameter. In addition, the closed NTC offered the maximal increase in flexion stiffness of the construct with thick rods and 10-, 15-, and 20-cm-long rods at a maximum of 40%, 27%, and 30%, respectively. This rigid closed NTC increased the extension stiffness of the same construct with 10- and 15-cm-long rods at 40% and 6%, respectively, whereas it had no influence on the extension stiffness of 20-cm-long rods.

Medium- and long-term results of high tibial osteotomy for varus gonarthrosis in an agricultural population.

High tibial valgus osteotomy for varus gonarthrosis was performed in 63 consecutive patients in a homogenous agricultural population using two different surgical techniques. Patients were divided into two groups. A two-level Mittelmeier osteotomy was performed in group A patients, and a lateral closed wedge high tibial osteotomy using the AO/ASIF L-plate was performed in group B patients. Operations were performed by two different groups of surgeons. Patients were evaluated postoperatively for correction of knee axis, functional result, subjective impression, and complications. In group A patients, 80% of the operated knees were corrected to the mechanical axis and in group B patients, 82% of the knees were corrected to 6 degrees-10 degrees valgus of the anatomical axis. Ninety percent, 70%, and 54% of group A and 91%, 73%, and 57% of group B patients were rated as satisfactory results at 5, 9, and 12 years postoperatively, respectively; these differences were not statistically significant. One year postoperatively, 91% of group A and 96% of group B patients reported their symptoms had improved. However, patient satisfaction decreased at 5, 7, and 12 years postoperatively, with 91%, 89%, and 66% of group A and 96%, 93%, and 68%, respectively, of group B patients reporting their symptoms had improved; these differences were not statistically significant. Postoperatively, most patients returned to full agricultural activity. Total knee arthroplasty, which was later required in 12% of the knees, was not significantly jeopardized by the previous osteotomy.

Mueller roof reinforcement rings. Medium-term results.

Short term results of cemented acetabular reconstruction with the use of the Mueller reinforcement ring in 30 hips in 29 patients have been reported previously. The indications for reinforcement were primary and postrevision segmental, cavitary, and combined acetabular deficiencies. The current study reports the medium term clinical and radiologic results of 20 of the 29 patients who were surgically treated (18 primary and eight postrevision hips) and who underwent followup with detailed clinical and radiographic analysis within an average of 9 years (range, 7-12 years). In the latest followup, there has been a statistically insignificant decrease in clinical scores compared with those obtained immediately after surgery; the changes probably are a result of the patients' aging. The radiologic scores at the latest followup were lower, although not statistically significant, than those at the short term followup. The causes of the three ring failures that occurred 5, 8, and 8.5 years after surgery and required revision arthroplasty were either acute trauma or tuberculous arthritis. Three additional hips (two primary and one revision) had evidence of loosening in the ring and socket associated with symptomatology and were considered as hips with impending revision. The rate of success of primary implantation was 94% at 7 years, 86% at 10 years, and 86% at 12 years and was not statistically different from that of revision implantation, which was 86% in all three followup periods. In this small series this surgical technique was successful and effective and followed by good medium term clinical and radiographic results in primary and revision implantation in segmental, cavitary, or complex acetabular deficiencies and in osteoporotic or deficient acetabular bone.

Segmental roentgenographic analysis of vertebral inclination on sagittal plane in asymptomatic versus chronic low back pain patients.

Two homogenous groups of 120 volunteers and 120 low back pain (LBP) patients, age range 20-79 years, underwent a prospective roentgenographic segmental vertebral analysis of the thoracic and lumbar spine to compare several roentgenographic parameters useful for planning spine surgery. The following roentgenographic parameters were measured: thoracic kyphosis, lumbar lordosis, sacral inclination, distal lordosis (L4-S1), inclination of each vertebra from T4-S1, and relative vertebral inclination between adjacent vertebrae. Thoracic kyphosis increased (p < 0.0001) and sacral inclination decreased (p < 0.05) with age in the control group. Increased thoracic kyphosis correlated with decreased lumbar lordosis after the sixth decade in the control group (p < 0.01), less so in the LBP group (p < 0.05). Increased thoracic kyphosis was seen more in the LBP group than in the controls, but significantly solely in the sixth decade (p < 0.01). Lumbar lordosis was more increased in the controls than in the LBP group but significantly solely in the sixth decade (p < 0.001). The L5-S1 segmental lordosis was much more in the LBP patients than in the controls (p < 0.001). Lumbar lordosis was strongly correlated with sacral inclination in both groups (p < 0.0001) and it was significantly greater in the controls, particularly in the sixth decade (p < 0.001). Sacral inclination was significantly more in the female than in male volunteers (p < 0.05). Distal lordosis (L4-S1) represents 55% and 49% of total lumbar lordosis in controls and low back patients, respectively. Spine surgeons frequently deal with sagittal spinal deformities and the deviations of sagittal spinal curvatures and vertebral inclination in the sagittal plane, both in normal subjects and LBP patients should be clinically helpful.

First experience with the use of compression cerclage Gundolf in orthopaedic and trauma surgery. A preliminary report.

In this prospective study we describe our experience with a new method of osteosynthesis of fissures, spiral and comminuted fractures of long bones of the extremities using the titanium compression cerclage of Gundolf (CCG). The operative technique is described in detail, and the results are presented for 50 operated patients who were followed up until fracture consolidation. The technique of application of the CCG is simple and quick and according to the results obtained ensures a permanent fixation at the site of the fracture. No cerclage-related complications such as stress shielding, corrosion, breakage of the band and impairment of the superficial cortical blood supply were radiologically observed in this series. We recommend the use of this titanium band in difficult cases of fractures of the long bones as well as in selected cases of primary and particularly revision hip arthroplasty.

Monoradiculopathy of the fifth lumbar nerve root due to lumbar disc herniation between lumbar one and lumbar two vertebrae.

An extremely rare case is reported of a 34-year-old man who had a drop foot due to a herniated disc between the first and second lumbar vertebrae with a monoradiculopathy of the fifth lumbar nerve root. The diagnosis was made on the basis of myelography and magnetic resonance imaging (MRI), which revealed a disc centrolateral herniation at the level between the first and second lumbar vertebrae. The patient underwent anterior discectomy and fusion with the use of iliac bone graft. Because of increasing local kyphosis and associated symptoms, a posterior TSRH instrumentation was added successfully. Postoperatively the patient had alleviation of his symptoms, and at the 6-year follow-up evaluation, he was completely symptomless. The spine surgeon should be aware of the possibility of this rare location of lower lumbar nerve root compression within the dural sac. In such a case, myelography and MRI seemed to be superior to the computed tomography scan.

Unrecognized laceration of main bronchus caused by fracture of the T6 vertebra.

We report on an extremely rare case of a 58-year-old male polytraumatized patient who sustained a bursting fracture of the T6 vertebral body associated with laceration of the posterior wall of the right main bronchus from the spiculae of the vertebral body fragments. The patient was on admission asymptomatic until he underwent an endotracheal anesthesia for stabilization of associated fractures of the extremities, when he developed acute respiratory disturbances. The opening of the bronchus was repaired via a thoracotomy, while the spine was successfully supported with a custom-made brace for 3 months. In the 3-year follow-up evaluation, the patient did well and suffered no complaints of the spine or lungs. Spine surgeons should be aware of this rare complication, which may accompany bursting fractures in the midthoracic spine. Laceration of the bronchus should be suspected when fragments of the vertebral body are dislocated far anteriorly.

Reciprocal angulation of vertebral bodies in the sagittal plane in an asymptomatic Greek population.

STUDY DESIGN: A prospective study conducted on several roentgenographic parameters of the standing sagittal profile of the spine in an asymptomatic Greek population. OBJECTIVES: To perform segmental analysis of the sagittal plane alignment of the normal thoracic, lumbar, and lumbosacral spines and to compare the findings with those derived from similar populations. SUMMARY OF BACKGROUND DATA: Until recently, little attention has been paid to the sagittal segmental alignment of the spine, and there are only a few studies (in French and American populations) in which radiographic analysis of sagittal spinal alignment is investigated. METHODS: Ninety-nine consecutive asymptomatic Greek volunteers (38 men, 61 women), an average age of 52.7 +/- 15 years old (range, 20-79 years), were included in this prospective study, on the basis of several inclusion criteria. These volunteers were divided into six distinct age groups. The radiologic parameters, which were measured (by Cobb's method) on the lateral standing roentgenograms of the whole spine were: thoracic kyphosis (T4-T12), lumbar lordosis (L1-L5), total lumbar lordosis (T12-S1), distal lumbar lordosis (L4-S1), sacral inclination (measured from the line drawn parallel along the back of the proximal sacrum and the vertical line), pelvic tilting, vertebral body inclination, and relative segmental inclination between pairs of adjacent vertebrae. RESULTS: Thoracic kyphosis and lumbar lordosis (T12-S1, L1-L5) were not gender related. Thoracic kyphosis increased with age (P < 0.001), the lumbar spine (L1-L5) gradually became less lordotic as the thoracic kyphosis increased (P < 0.003), and total lumbar lordosis was not age related. Sacral inclination correlated strongly with both thoracic kyphosis (P < 0.002) and L1-L5 lordosis (P < 0.001). Pelvic tilting correlated strongly with L1-L5 lordosis (P < 0.0075), but did not correlate with thoracic kyphosis and age. Vertebral body inclination showed a narrow variability in T6-T12 and in L4 and a wide variability in T4, T5, L1-L3, and S1. Distal lumbar lordosis represents the 68.6% of the total lumbar lordosis. CONCLUSIONS: In the results of this study, a reliable table of reference for roentgenographic parameters in the sagittal plane of the spine was established in an asymptomatic Greek population. The parameters are similar to those used in previous studies. Thus, these data should be considered in preoperative planning and postoperative evaluation of achieved correction during restoration procedures of the spine in the sagittal plane.

Transthoracic disc excision with interbody fusion. 12 patients with symptomatic disc herniation followed for 2-8 years.

Thoracic disc herniation is a rare and slowly progressing disease, commonest at the lower thoracic spine. We performed transthoracic discectomy and interbody fusion in 12 patients with an average age of 46 years suffering from symptomatic herniated thoracic disc. Pain and neurologic impairment were the commonest symptoms at admission. The outcome at a mean follow-up of 4 (2-8) years concerning pain were excellent or good in 10 patients, fair in 1 and unchanged in 1 patient. There were no approach-related complications. All 7 patients with incomplete neurologic impairment preoperatively improved postoperatively at least 1 Frankel grade. Posterior complementary fusion at the thoracolumbar junction was necessary in 2 patients because of increasing symptomatic local kyphosis. Although the number of patients is small, due to the rarity of the disease, it seems that the transthoracic approach for anterior discectomy and fusion is an appropriate treatment for symptomatic thoracic disc herniation. Proper patient selection, preoperative planning and surgical technique resulted in good pain relief, neurologic recovery in cases associated with incomplete neurologic impairment and restoration of the sagittal profile of the thoracolumbar spine.

Use of the Texas Scottish Rite Hospital instrumentation in the treatment of thoracolumbar injuries.

STUDY DESIGN: This is a prospective study of the results of the use of Texas Scottish Rite Hospital instrumentation for thoracolumbar and lumbar injuries. To make an objective assessment of the clinical and radiologic results, the second and the third authors were used as unbiased assessors. OBJECTIVES: To evaluate the short-term results of the use of Texas Scottish Rite Hospital instrumentation in thoracolumbar injuries. SUMMARY OF BACKGROUND DATA: To the authors' knowledge, there are only a few reports concerning the use of the Texas Scottish Rite Hospital instrumentation for stabilization of the spine, mostly in scoliosis and degenerative spine disease, and only one report on use of this instrumentation in thoracolumbar injuries. METHODS: Forty patients, with an average age of 45 years, who suffered from 48 thoracolumbar spinal fractures and dislocations, underwent posterior Texas Scottish Rite Hospital hook-rod instrumentation by means of "double-claw" configuration, two levels above and two below the lesion level for reduction of the injury, and stabilization and restoration of the sagittal profile of the thoracolumbar spine. Roentgenograms and computed tomography scans were evaluated on the basis of the same protocol before and after surgery and in follow-up observation. RESULTS: All patients were followed for an average period of 32 months. The sagittal profile of the thoracolumbar spine was restored significantly. No patient had neurologic deterioration after surgery, and all patients with incomplete lesions improved postoperatively at least one Frankel grade. One hook dislodgment was observed in one patient without loss of correction or non-union. There was only one deep infection. CONCLUSIONS: With the Texas Scottish Rite Hospital instrumentation, it was possible to provide solid internal fixation with restoration of the sagittal profile without loss of correction.

Three-level thoracic disc herniation: case report and review of the literature.

A rare case of three-level thoracic disc herniation with associated neurological impairment, including motor, sensor and urinary disturbances, is reported. The diagnosis and localization of the level of cord compression were mainly based on the clinical examination supported by the findings of magnetic resonance imaging and somatosensory evoked potentials. An anterolateral transthoracic approach at the upper-most affected level was selected for removal of all herniated discs, with the use of a surgical microscope; the resected rib was used for intervertebral fusion. An improvement in the patient's subjective and neurological condition was already apparent a few months after the operation, and solid fusion was roentgenographically found at all operated levels. The use of a surgical microscope allows complete removal of the herniated disc while avoiding wide vertebrectomy and associated iatrogenic damage to the spinal cord.

Course of bone mineral content changes around cementless Zweymueller total hip arthroplasty. A 4-year follow-up study.

In this prospective study we followed the bone mineral content (BMC) changes over time in seven zones of interest around uncemented Zweymueller total hip arthroplasty (THA) components, using dual-energy X-ray absorptiometry (DEXA) combined with a radiographical analysis of the distal femoral cortices, close to the tip of the stem. In 36 women (average age 55 years) operated on for primary hip osteoarthritis, BMC of the hips was measured preoperatively and 2 weeks, 1 year and 4 years postoperatively. In particular, a significant decrease of the preoperative values (ranging from 35% to 42.53%; P = 0.05 to 0.01) was noted immediately postoperatively in zones 2-7. Thereafter, an additional significant increase of BMC was observed between the first and last observations at the greater (30%, P < 0.05) and lesser (35.48%, P < 0.01) trochanter. The BMC changes over time were not related to the age of the patients. The BMC reduction observed immediately after implantation of the Zweymueller THA is probably related to the intraoperatively removed bone from (1) the medial and distal inner surface of the acetabulum and (2) the inner femoral cortex. Thereafter, the BMC in zones 2, 6 and 7 remained practically unchanged. The fact that a significantly delayed BMC increase was found in the region of the greater and minor trochanter 4 years later may be due to an increasing, continuous bone turnover in the intertrochanteric area. Thus, the Zweymueller screw socket becomes definitively anchored immediately postoperatively in the medial and distal thirds of the acetabulum and remains stable over time, whereas the Zweymueller stem is mainly anchored within the distal femoral cortex as well as within the mass of the greater and minor trochanter, and was still stable at the 4-year follow-up.

Changes in bone mineral density around a stable uncemented total hip arthroplasty.

Changes in bone mineral density (BMD) around the components of the Zweymueller total hip arthroplasty were measured, using dual energy X-ray absorptiometry, in 36 women who were operated on for primary osteoarthritis. Seven regions of interest were studied. No changes occurred around the screw socket and the greater trochanter: but there was a significant reduction of BMD, only when measured immediately after the operation at the lesser trochanter and at the distal femoral cortex lateral and medial to the tip of the stem. These changes were not related to the age of the patients. The reduction of BMD in the femur was mostly associated with areas where bone had been removed at operation. The press-fit fixation of the Zweymueller stem and the maintenance of its fixation with time did not induce further bone turnover around it. The absence of changes in bone mineral density was due to the relatively small amount of subchondral removed and to the continued stable fixation of the socket.