Tibial post wear in posterior-stabilized knee replacements is design-dependent.

Polyethylene tibial post wear in posterior-stabilized knee designs is a major problem. The Insall-Burstein II (IB PS II) reportedly has severe anterior wear of the post in retrieved implants. We hypothesized the more anterior placement in the IB PS II would be reflected in greater wear at the anterior face than the IB PS I. We examined 234 retrieved inserts using subjective scales to grade post damage and wear. Of the IB PS II inserts, 38% demonstrated severe wear compared with only 25% of IB PS I inserts. The most prevalent damage location for the IB PS II was the anterior face, whereas the IB PS I sustained wear mainly on the medial face. While the IB PS post was not designed to constrain posterior femoral displacement, our observations confirm contact in hyperextension or other paradoxic anterior tibial translation is common and design-dependent. Minimizing wear and damage through proper post placement and changes in implant design to anticipate contact on the anterior post should be considered for future posterior stabilized knee replacements. These changes cannot occur in isolation, however, because changes in post placement and design also depend on their relation to the shape and location of the tibial bearing surfaces.

Total knee arthroplasty in patients with poliomyelitis.

Between 1991 and 2001, 17 primary total knee arthroplasties were performed in 15 patients with limbs affected by poliomyelitis. Eight patients had a constrained condylar knee design, 8 a posterior stabilized design, and 1 a hinged design. Mean follow-up was 41.5 months. The mean Knee Society knee score improved from 45 preoperatively to 87 postoperative. Knee stability was obtained in all patients, including 4 patients with less than antigravity quadriceps strength. Radiologic evaluation showed satisfactory alignment with no signs of loosening. Complications included 1 case of deep venous thrombosis and 2 knees that required a manipulation for stiffness. Pain relief, functional improvement, and knee stability can be achieved after constrained total knee arthroplasty in patients with poliomyelitis despite impaired quadriceps strength, and osseous and soft tissue abnormalities.

Impingement contributes to backside wear and screw-metallic shell fretting in modular acetabular cups.

Eighty-six polyethylene liners and 56 metallic shells of acetabular components were evaluated by visual and stereomicroscopic examination for impingement, backside polyethylene wear, creep, and fretting at the screw-metallic shell interface using a subjective scoring system. Medical records and radiological data were available in 65 and 46 patients, respectively. Impingement was found in 62 components (75%). Backside polyethylene wear and screw-metallic shell corrosion and fretting were significantly correlated (P < .001) with impingement. Polyethylene creep was significantly correlated to backside wear and tended to be higher for the cups that had impingement (P = .06). No correlation was found between backside polyethylene wear and implant design or cup position. Our results suggest that impingement in a modular acetabular component correlated with increased backside wear and screw-metallic shell corrosion and fretting.

An incidental finding of chondroid lipoma at total hip arthroplasty.

Chondroid lipoma is a rare benign lipomatous soft tissue tumor which presents as a painless lump. This case report presents the incidental finding of such a tumor at total hip replacement and briefly reviews the literature regarding the histopathological features of this recently described neoplasm.

Cortical and cancellous morselized allograft in acetabular revision total hip replacement: minimum 5-year follow-up.

Sixty patients who had had revision acetabular components with impaction morselized bone graft were studied in a retrospective, matched-pair analysis. In 30 patients, the morselized graft was derived from cortical bone (group A), and in 30 patients, the graft was derived from cancellous bone (group B). The patients were matched for age, gender, weight, comorbid conditions, Charnley category, severity of bone loss, and allograft preparation. At the time of follow-up, a mean of 7.4 years (range, 5-9 years) after surgery, the mean Harris Hip Scores in groups A and B were 84 and 77, respectively. Cup migration of 5 to 10 mm were noted in two patients in each group. Cup migration >10 mm was noted in 2 patients from group B and none in group A. Two patients in group A and 5 patients in group B underwent cup rerevision as a result of aseptic loosening. There was a correlation between progressive radiolucent lines extending 2 mm, cup migration, and clinical outcome. The current study showed that early and midterm clinical and radiologic outcomes such as cup migration >5 mm and radiolucent lines were significantly better using cortical morselized allograft. However, further mechanical and histologic evaluations should be performed that demonstrate the difference between these 2 types of morselized allograft.

Cancellous and cortical morselized allograft in revision total hip replacement: A biomechanical study of implant stability.

To restore femoral intramedullary bone stock loss in revision surgery of failed total hip arthroplasties, impacted morselized cancellous allograft is recommended. This study investigated the mechanical properties of both impacted cortical (group A) and cancellous (group B) morselized bone graft for reconstruction of femoral bones. Ten matched pairs of fresh frozen human femora were prepared by over-reaming to create a smooth-walled cortical shell. Each pair had one cortical and one cancellous impacted morselized allograft and cement. Stem subsidence was evaluated by a cyclic axial load, which was applied by a servohydraulic test. The stem subsidence was measured for initial subsidence (subsidence at the first 1000 cycles), the total axial subsidence (subsidence at the end of cycles under load) and the final axial subsidence (subsidence after the unloading phase). Torque test was measured by torsional loads through the prosthetic femoral heads. Total axial subsidence was significantly higher in group B (mean: 1.32+/-0.32 mm) compared to group A (mean: 0.94+/-0.26 mm) (P<0.01). There was no significant difference between the two groups in terms of initial subsidence (P=0.09) and final axial subsidence. The mean maximum torque before failure was 39.5+/-22.2 N-m for the cortical morselized allograft and 32.5+/-18.1N-m for cancellous. We concluded that impacted morselized cortical bone graft used for reconstruction of contained femoral bone loss in revision hip arthroplasty, may reduce the stem subsidence. Further animal experimentation for mechanical and histological evaluation of in vivo application is warranted.

Cortical and cancellous morselized allograft in revision total hip replacement.

Fifty patients who had revision femoral components with morselized impacted bone graft were studied in a retrospective, matched-pair analysis. In 25 patients the morselized graft was derived from cortical bone (Group A) and in 25 patients the morselized graft was derived from cancellous bone (Group B). The patients were matched for age, gender, weight, comorbid conditions, severity of bone loss, and allograft preparation. At a mean of 5.2 years followup (range, 3-7 years) after surgery, the mean Harris ?hip score and the mean thigh score in Group A was 88 and 1.2 points, respectively, and in Group B was 88 and 2.3 points, respectively. Subsidence greater than 5 mm and radiolucent lines on more than 20% of the stem interfaces were seen in fewer patients from Group A (three and two patients) than from Group B (eight and five patients). There was a correlation between radiolucent lines on more than 50% of the stem, stem subsidence, and thigh pain. The current study showed significantly better results using morselized cortical allograft when assessed by early clinical outcome, thigh pain, and stem subsidence greater than 5 mm.

Intra-synovial, compared to intra-articular morphine provides better pain relief following knee arthroscopy menisectomy.

PURPOSE: To evaluate the analgesic effect of morphine 1 mg administered into the synovial tissue and the outer third of the meniscus after knee arthroscopy. METHODS: In a prospective, double-blind, randomized study, 60 patients who required elective knee arthroscopy were assigned to two groups: Group A consisted of 30 patients who received a direct injection of morphine 1 mg into either the synovial tissue or the outer third of the meniscus following menisectomy. Group B consisted of 30 patients who received a direct injection of NaCl 0.9% 1 mL into the synovial tissue or the outer third of the meniscus following menisectomy. At the end of the operation Group A received an intra-articular injection of NaCl 0.9% 1 mL and bupivacaine 0.5% 10 mL and Group B received an intra-articular injection of morphine 1 mg and bupivacaine 0.5% 10 mL. Analgesic effect was evaluated by pain intensity (visual analogue scale; VAS) and analgesic requirements (paracetamol) during the first one, three, six, 12, 24, and 48 hr postoperatively. RESULTS: There was no significant difference between the two groups within the first six hours and after 24 hr following the operation regarding VAS score and analgesic requirements. At 12 and 24 hr following the operation, the VAS score and the analgesic requirements were significantly higher in Group B compared to Group A (P <0.01 and P <0.01, respectively). No patient developed side effects. CONCLUSION: We conclude that direct morphine injection into the synovia or the outer third of the meniscus provided better pain relief than intra-articular morphine after knee arthroscopy.