Panayiotis J. Papagelopoulos

Hip and knee replacement in osteogenesis imperfecta.

Five total hip and three total knee arthroplasties were performed, from 1969 to 1990, in six patients who had osteogenesis imperfecta. The patients who had a hip arthroplasty were followed for a mean of seven years, and those who had a knee arthroplasty, for a mean of ten years. Postoperatively, all had relief of pain and were able to walk; one patient used a walker and two used a cane. The only postoperative complication was an intrapelvic protrusion of the acetabular component six years after a bipolar hip replacement.

Treatment of Aneurysmal Bone Cysts of the Pelvis and Sacrum

Background: Aneurysmal bone cysts are benign, non-neoplastic, highly vascular bone lesions. The purpose of this study was to describe the prevalence, the clinical presentation, and the recurrence rate of aneurysmal bone cysts of the pelvis and sacrum and to examine the diagnostic and therapeutic options and prognosis for patients with this condition. Methods: Forty consecutive patients with an aneurysmal bone cyst of the pelvis and/or sacrum were treated from 1921 to 1996. Their medical records and radiographic and imaging studies were reviewed, and histological sections from the cysts were examined. Seventeen lesions were iliosacral, sixteen were acetabular, and seven were ischiopubic. Seven involved the hip joint, and two involved the sacroiliac joint. All twelve sacral lesions extended to more than one sacral segment and were associated with neurological signs and symptoms. Destructive acetabular lesions were associated with pathological fracture in five patients and with medial migration of the femoral head, hip subluxation, and hip dislocation in one patient each. The mean duration of follow-up was thirteen years (range, three to fifty-three years). Results: Thirty-five patients who were initially treated for a primary lesion had surgical treatment (twenty-one had excision-curettage and fourteen had intralesional excision); two patients also had adjuvant radiation therapy. Of the thirty-five patients, five (14%) had a local recurrence noted less than eighteen months after the operation. Of five patients initially treated for a recurrent lesion, one had a local recurrence. At the latest follow-up examination, all forty patients were disease-free and twenty-eight (70%) were asymptomatic. There were two deep infections. Conclusion: Aneurysmal bone cysts of the pelvis and sacrum are usually aggressive lesions associated with substantial bone destruction, pathological fractures, and local recurrence. Current management recommendations include preoperative selective arterial embolization, excision-curettage, and bone-grafting.

Biomechanical evaluation of posterior screw fixation in cadaveric cervical spines

Sixteen fresh-frozen spines from cadavers (C4–T1) were randomized on the basis of dual energy xray absorptiometry analysis of bone mineral density. The specimens were subjected to physiologic loads (≤ 1.5 N-m) in a device that applied pure unconstrained, flexion and extension, lateral bending, and torsional moments. After a major injury, including a wide C6 laminectomy, bilateral capsulectomies, and 65% facetectomy at C6–C7, four constructs were applied to each specimen in a balanced sequence, and the stability tests were repeated. All the constructs were identical posterior cervical rods secured to the spine with lateral mass screws in C5 and pedicle screws in C7. The constructs differed only in the presence or absence of a transverse connector between the rods, presence or absence of lateral mass screws in C6, and unicortical or bicortical lateral mass screws. Insertional screw torque was higher in specimens with greater bone mineral density. Pedicle screws had greater torque than lateral mass screws. Posterior cervical spine rod fixation provided an equivalent stability by use of either unicortical or bicortical lateral mass screws. A transverse stabilizer between the rods reduces the number of lateral mass screws needed in posterior cervical spinal rod systems. Repeated stability tests, even when done with physiologic loads, may compromise the screw-bone interface. This effect is most pronounced in specimens that have low bone mineral density.

Acetabular reconstruction using bipolar endoprosthesis and bone grafting in patients with severe bone deficiency

Eighty-one patients who had hip reconstruction with bone grafting and bipolar endoprosthesis for severe acetabular deficiency were reviewed retrospectively at 3 to 8 years postoperatively. Failed total hip arthroplasty was the most common indication for operation. Bone grafts were fixed bone blocks, morselized cancellous bone, and wafer-type grafts used singly or in combination. The average Harris hip rating score was 49.9 points preoperatively, 81.4 points at 1 year, and 70.8 points at latest followup examination. The 35 unsuccessful procedures included 25 reoperations for implant removal (resection arthroplasty or revision) and 10 cases pending revision. At latest followup examination, 54.7% of patients considered themselves improved and 62.7% had no or mild pain. Eighty-five percent of cases had radiographic evidence of component migration that was superior and medial in direction. Overall probability of implant survival was 96% at 1 year, but only 47% at 6.5 years postoperatively. Because of the high failure rate, this procedure has a limited role in hip reconstruction, but may be a reasonable part of a staged reconstruction for patients with massive bone loss or in certain revision cases where instability is a concern.

Biomechanical evaluation of occipital fixation

Many studies have shown a positive correlation among screw pullout strength, screw insertional torque, bone thickness, and areal bone mineral density (BMD) measured by dual-energy X-ray absorptiometry. Variations are significant in the anatomy of the occipital bone. But no studies have correlated these variables with respect to the two locations commonly used for plate fixation to the occiput. The purpose of this study was to determine the thickness and quality of the occipital bone and to correlate these variables with the insertional torque of screws and the pullout strength of plates secured into two different locations on the occiput. The occiputs of 12 adult human fresh frozen cadaveric specimens were used. The specimens were analyzed by dual-energy X-ray absorptiometry. Direct thickness measurements of the occiput were performed. Areal and volumetric BMD were measured. A simple pelvic reconstruction plate (3.2 mm) was fixed to the occiput either laterally or at the midline with bicortical 4-mm cancellous screws. Torque was recorded at the time of insertion of each screw. Axial pullout tests were performed on all specimens. The peak load, failure load, stiffness, and energy to failure were recorded for each construct. Statistical analysis showed that the average thickness of occipital bone is greater in the midline than laterally. Occipital bone is thicker and screw torque is greater close to the inion. There is a positive correlation between bone thickness, areal BMD as measured by dual-energy X-ray absorptiometry, screw insertional torque, and strength of fixation. A plate fixed in the midline region of the occiput provides more rigid fixation than a plate fixed laterally. Areal BMD correlates better than volumetric BMD with bone thickness and is a reliable predictor of the strength of occipital fixation.

Prosthetic hip replacement for pathologic or impending pathologic fractures in myeloma

The authors retrospectively reviewed 53 hip replacements performed in 50 patients (mean age, 65 years) for plasmacytoma (four lesions) or multiple myeloma (49 lesions) of the hip region. Perioperatively, 49 patients received chemotherapy. Twenty-four hip lesions had radiation therapy. Within a mean followup period of 32.6 months, 15 (28%) complications occurred. Late deep infection, dislocation, and aseptic loosening with medial migration of the acetabular component occurred in one patient each. Three patients died during the first postoperative month. All of the remaining patients postoperatively regained their previous ambulatory status; hip pain relief was achieved in 98% of patients. At the time of the latest followup evaluation, 84% of the patients had died (median survival time, 18 months) and 16% were still alive (median survival time, 76 months). Patients with plasmacytoma had longer survival than did patients with multiple myeloma (median survival, 6.3 years versus 18 months, respectively). No significant association was found between patient survival and the stage of disease at diagnosis, age, gender, type or location of the myeloma lesion, or the type of implant used. Because of the relatively long survival time, prosthetic replacement is indicated for extensive hip lesions in patients with plasmacytoma or multiple myeloma.

Biomechanical evaluation of new posterior occipitocervical instrumentation system.

Twelve fresh-frozen cadaveric occipitocervical specimens were randomized based on dual energy xray absorptiometry analysis of bone mineral density. The specimens were subjected to physiologic loads in a device that applied pure unconstrained flexion and extension, lateral bending, and axial rotational moments. The spines were tested intact and after major injury simulating transoral decompression of the dens. Biomechanical testing using pure moments with physiologic loads (< 1.5 N-m) was used to compare stability of posterior occipitocervical plates and screws, loop and cable construct, and new cervical rod and screw system. The injury created significantly less stiffness and greater range of motion and neutral zone at C1–C2 in flexion and extension and lateral bending and greater range of motion and neutral zone in axial rotation than the intact state. In lateral bending, the new rod construct had significantly lower mean values for range of motion than the loop and the plate construct. In axial rotation, the rod construct had a significantly higher mean value for stiffness than the other two devices and a significantly lower mean value for range of motion than the loop. The new rod-based instrumentation system for occipitocervical fixation is biomechanically equivalent or superior to a plate and screw construct and a rod and cable system.

Vertebra plana caused by primary Ewing sarcoma: Case report and review of the literature

A 7-year-old boy presented with vertebra plana of T11. The presumptive diagnosis suggested by clinical presentation, conventional radiographs, and computed tomographic scans was eosinophilic granuloma. Progressive neurologic symptoms required surgical excision of the lesion and decompression. Histopathologic examination of the surgical specimen confirmed the diagnosis of Ewing sarcoma.