Comparison of the effect of posterior lumbar interbody fusion with pedicle screw fixation and interspinous fixation on the stiffness of adjacent segments / 中华医学杂志(英文版)

<p><b>BACKGROUND</b>Adjacent segment degeneration could seriously affect the long-term prognosis of lumbar fusion. Dynamic fixation such as the interspinous fixation, which is characterized by retaining the motion function of the spinal segment, has obtained satisfactory short-term effects in the clinical setting. But there are few reports about the biomechanical experiments on whether dynamic fixation could prevent adjacent segment degeneration.</p><p><b>METHODS</b>The surgical segments of all 23 patients were L4/5. Thirteen patients with disc herniation of L4/5 underwent Wallis implantation surgery, and 10 patients with spinal stenosis of L4/5 underwent posterior lumbar interbody fusion (PLIF). L3-S1 segmental stiffness and displacement were measured by a spine stiffness gauge (SSG) device during surgery when the vertebral plate was exposed or during spinal decompression or internal fixation. Five fresh, frozen cadavers were used in the self control experiment, which was carried out in four steps: exposure of the vertebral plate, decompression of the spinal canal, implantation of a Wallis fixing device, and PLIF of L4/5 after removing the Wallis fixing device. Then, L3-S1 segment stiffness was measured by an SSG device.</p><p><b>RESULTS</b>The experiments showed that the average stiffness of the L4/5 segment was (37.1 ± 8.9) N/mm after exposure of the vertebral plate, while after spinal decompression, the average stiffness fell to (26.2 ± 7.1) N/mm, decreasing by 25.8% (P < 0.05). For the adjacent segments L3/4 and L5/S1, their stiffness showed no significant difference between the L4/5 segment decompression and the exposure of the vertebral plate (P > 0.05). After Wallis implantation of L4/5, the stiffness of the cephalic adjacent segment L3/4 was (45.8 ± 10.7) N/mm, which was 20.5% more than that after the exposure of the vertebral plate (P < 0.05); after L4/5 PLIF surgery, the stiffness of L3/4 was (35.3 ± 10.7) N/mm and was decreased by 12.4% more than that after the exposure of the vertebral plate (P < 0.05). The stiffness of the cephalic adjacent segment L3/4 after fixation in the Wallis group was significantly higher than that of the PLIF group (P < 0.05). Cadaver experiments showed that the stiffness of the cephalic adjacent segment in the Wallis group was significantly higher than that of the PLIF group after L4/5 segment fixation (P < 0.05); the stiffness of the L5/S1 segment showed no significant difference between PLIF surgery and Wallis implantation (P > 0.05).</p><p><b>CONCLUSIONS</b>After interspinous (Wallis) fixation, the stiffness of the cephalic adjacent segment increased. After PLIF with pedicle screw fixation, the stiffness of the cephalic adjacent segment decreased. An interspinous fixation system (Wallis) has a protective effect for cephalic adjacent segments for the immediate post-operative state.</p>

Acetabular revision using acetabular reinforcement cages with a hook / 中华外科杂志

<p><b>OBJECTIVE</b>To evaluate the effects of cementless revising cup or acetabular reinforcement cages for reconstructing the massive acetabular deficiency.</p><p><b>METHODS</b>From September 2001 to September 2008, 22 loosening acetabular cases (24 hips) were revised using cementless revising cup or acetabular reinforcement cases for reconstructing massive bone defect after particulate bone grafting. There were 2 cases (2 hips) using Lima cementless revising cup, 2 cases (2 hips) using Kerboull ring, and 18 cases (20 hips) using restoration GAP cages. Six cases (6 hips) were male, and 16 cases (18 hips) were female. The mean age was 62 years old (34 - 79 years old). Septic loosening was in 2 cases (2 hips), and aseptic loosening in 20 cases (22 hips). The mean follow-up was 48 months (18 - 84 months).</p><p><b>RESULTS</b>There was no clinical or radiological evidence of loosening for the revising acetabular components at the last follow-up point. The mean Harris hip score was improved significantly from 56 points (44 - 75) before revision to 89 points (78 - 94) at the last follow-up after revision. Excellent and good rate was 95.5% (21/22 cases). The average abduction angle of the three types of acetabular reconstructive cages were 50.1 degrees (39.0 degrees - 66.0 degrees), and almost all cases of the hip rotation center were restored after revision surgery. At the last follow-up, the reinforcement cages were no immigration and breakup, and there was no radiolucent line around the acetabular components. The bone graft integrated well into surrounding acetabular bone.</p><p><b>CONCLUSION</b>The method of revising the massive acetabular bone defect by cementless revising cup and acetabular reinforcement cages restores the normal hip rotation center, supplies the primary stability of the revising component, and protects the bone graft from mechanical overload during its revascularization phase, which is a reliable method for revising the massive acetabular deficiency after total hip arthroplasty.</p>

The etiologies and prevention of patellar instability after un-resurfaced total knee arthroplasty / 中华外科杂志

<p><b>OBJECTIVE</b>To investigate the etiologies and prevention of patellar instability after total knee arthroplasty (TKA).</p><p><b>METHODS</b>From September 1997 to April 2005, 94 patients (105 knees) underwent TKA without patellar resurfacing. All of them were osteoarthritis. Ten patients (14 knees) were performed with Rotation Knee (RK) prostheses. Forty patients were performed with mobile bearing TACK prostheses, and 44 patients with GEMINI prostheses. Subluxation and tilt of patella were evaluated by X-rays before or after operation.</p><p><b>RESULTS</b>The incidence of patellar instability after operation was 28.6% in patients who had genu valgus deformity, and was 29.5% in whom had patellar instability preoperative. The incidence of patellar instability in RK, TACK, and GEMINI group was 28.6%, 20.9%, and 16.7% respectively after operations. Four patients had obvious femoral or tibial components malrotation.</p><p><b>CONCLUSIONS</b>The etiologies of patellofemoral instability include pre-operative conditions, prosthetic design, and improper positioning of the prosthetic component. So the suitable component design and skillful operative technique will help the surgeon to avoid this complication.</p>

Change in the joint line after total knee arthroplasty / 中华外科杂志

<p><b>OBJECTIVE</b>To investigate the change in joint line after knee arthroplasty.</p><p><b>METHODS</b>A total of 43 patients had 25 primary cruciate-retaining total knee replacements (Link Gemini MKII) and 25 rotational knee replacements (Link Endo-Model Rotational Knee System) sacrificing collateral ligaments and cruciate ligaments. Lateral radiographs were made both preoperatively and postoperatively. The change in the relative position of the joint line preoperatively and postoperatively was defined as the difference between the perpendicular distance from the weight-bearing surface of the tibial plateau to the tibial tubercle of the natural tibia (JL) and perpendicular distance from the weight-bearing surface of the prosthetic tibial component to the tibial tubercle (JL'). This distance was JL'-JL. The statistical differences between 2 groups were analyzed.</p><p><b>RESULTS</b>The distance of JL'-JL was 2.0 mm (-1.3 - 7.2 mm) in 22 patients with Gemini replacement, whereas the distance was 3.1 mm (-1.5 - 12.3 mm) in the other patients with rotational knee system. The difference was significant.</p><p><b>CONCLUSIONS</b>If the collateral ligaments and cruciate ligaments are removed during the knee replacement operations, the prosthetic joint line is likely to be malpositioned proximally. The fibular styloid and medial or lateral epicondylar reference points can be used to determine proper position of the joint line during operation.</p>