Femoral Intramedullary Rod Research Articles

Inaccuracy of the intramedullary femoral guide: traditional instrumentation lacks precision and accuracy.

The purpose of the study was to utilize a large-scale biomorphometric computer tomography (CT) database to determine the desirable starting point and angle for placement of the femoral intramedullary rod in the sagittal plane. A CT-based modeling and analytics system (SOMA, Stryker, Mahwah, NJ) was used to evaluate 1029 entire-femur CT scans. From this, 19,464 simulations were run to test whether a 20cm intramedullary rod, with a radius of 4mm, would successfully pass through the femoral canal before contacting cortical bone. First, modelling included varying angles from 0-6 degrees in the sagittal plane, at 1-degree intervals. Next, the start point was adjusted with an assumed 3 degrees of induced flexion in comparison to the mechanical axis. A total of 5012 simulations were able to place the femoral intramedullary rod 20cm into the canal. The angle of the rod that created the highest proportion of successful jig placement was at a 3-degree angle of induced flexion to the orthogonal plane of the transepicondylar axis (TEA), with 33.7% successful jig placements. The starting point for the greatest proportion of successful guide placements was 48.5% along the distance between the sTEA, slightly closer to the lateral side. In the AP plane, the average distance to the ideal start point was 12.1mm anterior to the PCL. By examining over a thousand femoral CT scans, an angle of 3 degrees of induced flexion was identified in the sagittal plane with the highest proportion of successful placement of an intramedullary rod before cortical contact. It is important to note the high rate of failure in completely inserting the 20mm rod. This is a prospective computer based model.

Optimal Sagittal Insertion Depth and Direction of Femoral Intramedullary Rod in Total Knee Arthroplasty in Chinese Osteoarthritis Patients.

ObjectiveTo identify the optimal femoral intramedullary rod insertion depth and direction on the sagittal plane in total knee arthroplasty (TKA) of Chinese osteoarthritis (OA) patients.MethodsFrom January to December 2019, CT data were collected for 85 consecutive entire lower extremity Chinese OA patients. A three‐dimensional method was used to simulate intramedullary rod penetration. The intramedullary rods were inserted toward the anterior (TA), center (TC), and posterior (TP) of the femoral canal, respectively. Four penetration depths of 150, 200, 250, and 300 mm from the joint line were set. The intersection angle was measured between the simulated intramedullary rod and the mechanical axis of the femur (FMA) on the sagittal plane.ResultsOur study included 85 Chinese OA patients: 46 women, with a mean age of 65.7 ± 8.4 years (range, 51–85 years) and 39 men, with a mean age of 65.6 ± 8.1 years (range, 46–86 years). The intersection angle between the FMA and the femoral anatomical axis was smaller in men, 2.4° ± 1.6° (range, 0°–4.8°), than in women, 3.5° ± 2.3° (range, 0.7º–8.2°), with a significant statistical difference (P < 0.01). In the comparison of the intersection angle between the simulated intramedullary rod and the FMA, there was no statistical difference between TA200 and TC200 in women (P > 0.05). The proportions were up to 91% and 96% of TA200 at 0°–3° and 0°–5° intervals, respectively, but just 63% and 78% in TC200. In TA150, 76% of intersection angles were greater than 5°. Only approximately 60% in TA250 and TA300 were within the 0°–5° interval and 40% were less than 0°. Only 57% of intersection angles in TC150 were in the 0°–3° interval. TC250, TC300, and TP150 were mostly below 0°. In men, there were statistical differences between all groups. All intersection angles were greater than 5° in TA150. TA200 and TA250 were mostly greater than 5° (87% and 59%, respectively) and 72% of intersection angles were within 0°–5° interval in TA300. TC150 had 92% of intersection angles within the 0°–5° interval but only 62% between the 0° and 3° interval. In the TC200, up to 90% and 97% were within 0°–3° and 0°–5° intervals, respectively. TC300, TP150, and TP200 were mostly below 0°.ConclusionWe described an innovative method for rapidly, simply, and accurately identifying the sagittal insertion depth and direction of the femoral intramedullary rod in TKA, which can optimize the position of the femoral prosthetic component on the sagittal plane in TKA.

Accuracy of implantation of components in the Oxford knee using the minimally invasive approach

Screened postoperative X-rays of 224 Oxford knees implanted through the minimally invasive approach were analysed using 16 criteria. The technique was as recommended by the Oxford Group except that the femoral intramedullary rod was used only as a guide to flexion/extension of the femoral component. All femoral components were within the recommended range for varus/valgus and mediolateral position. Eighteen femoral components were either too flexed or extended, but by a maximum of only 10°. Tibial components were inserted in slight varus (mean 1.8°, S.D. 8.8, range 10 to −10). All were within the range for posterior slope in spite of difficulty in establishing objective landmarks. Tibial coverage was imprecise with the phase 3 implants which were short and broad relative to the cut surface. In 36% of knees the tibial tray was implanted too anterior resulting in posterior under hang. There have been no clinical signs to indicate tipping of the meniscus in deep flexion. The depth of cement penetration under the keel was excessive in three cases, resulting from porotic bone rather than technical error in the depth of the cut. There has been one case of femoral component loosening following a fall and no tibial loosening in spite of imprecise alignment of some components.

Sealing the intramedullary femoral canal with autologous bone plug in total knee arthroplasty

In a prospective study of 262 consecutive patients with total knee arthroplasty, we compared the postoperative suction drainage and transfusion requirement in cases in which the defect made by the femoral intramedullary rod was either unplugged (n = 134) or plugged (n = 128). All operations were performed with a single surgical approach and technique. Inflammatory arthritis and lateral releases were excluded. Blood loss was recorded at 24, 48, and 72 hours. The difference in postoperative suction drainage was not statistically significant. The hemoglobin decrease in the unplugged group (3.5 g/dL) was different from that in the plugged group (2.3 g/dL) (P<.05). Of patients, 64.4% (n = 85) in the unplugged group and 35.9% (n = 46) in the plugged group required transfusion (P<.05). Sealing the femoral canal is effective in reducing hemoglobin decrease and blood transfusion in total knee arthroplasty. Copyright 2003, Elsevier Science (USA). All rights reserved.

Plugging the intramedullary canal of the femur in total knee arthroplasty: Reduction in postoperative blood loss

A prospective, randomized trial comparing postoperative drainage was carried out in 120 consecutive knees undergoing total knee arthroplasties divided into 2 groups. In one (55 knees), the entry point for the femoral intramedullary rod was left open. In the other (65 knees), the entry point was closed by an autologous bone plug. The mean drainage after 24 hours and the total drainage were lower when the femoral canal was plugged (800 vs 960 mL and 925 vs 1,165 mL). The bone plug always united, and no loose bodies were seen 6 months after operation. We conclude that the femoral intramedullary guide hole should be plugged with autologous bone because this technique results in a small but significant reduction in early blood loss without countervailing disadvantages.

Secretory phospholipase A2 cleavage of intravasated bone marrow primes human neutrophils.

Recent clinical reports suggest that early femoral intramedullary rod (IMR) fixation in patients with multiple injuries increases the risk of adult respiratory distress syndrome (ARDS). We have shown that lipid-mediated neutrophil (PMN) priming and elevated circulating levels of secretory phospholipase A2 (sPLA2) within the first 24 hours after injury correlate with the development of ARDS. We thus hypothesized that circulating lipid products, generated by sPLA2 cleavage of intravasated bone marrow, prime PMNs for enhanced superoxide anion (O2-) production. Isolated PMNs from healthy volunteers were incubated for 5 minutes with buffer or sPLA2-lysed bone marrow (100 U/mL) collected from trauma patients. After formyl-methionyleucylphenylalanine (fMLP) activation, O2- production was quantified by the superoxide dismutase-inhibitable reduction of cytochrome c. Blood samples were also drawn from five injured patients before and 24 hours after femoral IMR fixation. PMNs were isolated and assessed for in vivo priming. PMNs incubated with sPLA2-lysed bone marrow were primed for more than 3.5 times greater fMLP-induced O2- production. Furthermore, in patients with femoral fractures, PMN O2- release in response to fMLP after IMR fixation was more than 2.5 times higher than before fixation. Collectively, the findings suggest that bone marrow released from acute fracture sites may become a lipid substrate for the elevated sPLA2 levels found in injured patients. The resultant priming of PMNs may thus render the injured patient at risk for ARDS. Although clearly hypothetical at present, we submit that these observations warrant further investigation because of their clinical implications.

A fluted femoral intramedullary rod. Biomechanical analysis and preliminary clinical results.

An intramedullary rod for the femur was designed and compared with rods commonly used. Its bending strength was increased 40 to 80 per cent and its torsional rigidity was increased 230 to 3,000 per cent compared with the other devices tested. In forty patients with traumatic and pathological fractures and osteotomies of the femur, excellent fixation was achieved and very early weight-bearing was possible. In all fresh fractures and non-infected non-unions, union occurred very promptly and bone-grafting was not required in most instances. The stregth and rigidity of the device made it exceptionally useful for non-unions, pathological fractures of the femur, and resection-fusions of the knee.