Douglas A. Dennis

Metal-on-Metal Total Hip Arthroplasty

Although metal-on-metal total hip arthroplasty (MOM THA) has been used for over 3 decades, substantial improvements in manufacturing and design have led to improved durability with modern implants. Reported advantages of the use of MOM THA include very low wear and subsequent osteolysis, increased range of motion to impingement secondary to the availability of larger diameter femoral heads, and the potential to monitor implant performance by serial assessment of metal ion levels. Clinical results of both first-generation and second-generation MOM THA have revealed good survivorship and a low incidence of osteolysis. Although the advantages of low wear and increased range of motion have made MOM THA an attractive bearing surface option, more widespread use of MOM bearing surfaces has been tempered with concern for increased metal ion levels and hypersensitivity reactions.

Femoral condylar contact points start and remain posterior in high flexing patients.

This study compares kinematic patterns of 136 patients following total knee arthroplasty with high post-operative knee flexion (HighFlex) versus kinematics of 114 patients with limited knee flexion (LowFlex) using a blocked stratified random sampling study design to reduce confounding and bias. The kinematics was collected using fluoroscopy and 2D to 3D registration for a weight-bearing deep knee bend activity. Both the lateral and the medial condylar contact positions for the HighFlex subjects were significantly more posterior than the LowFlex subjects at full extension and remained that way at all flexion angles. The amount translation of the contact points, axial orientation angle and axial rotation were found to be similar for the two groups. Lift-off was significantly higher in the LowFlex indicating mid-flexion instability.

What Preoperative Radiographic Parameters Are Associated With Increased Medial Release in Total Knee Arthroplasty

BACKGROUND Preoperative varus deformity of the knee is a common malalignment in patients undergoing primary total knee arthroplasty (TKA). We are unaware of any studies that have correlated how various preoperative radiographic parameters can predict the amount of medial releases performed to achieve optimal coronal alignment and ligamentous balance. METHODS A retrospective review was performed on 67 patients who required at least a medial tibial reduction osteotomy (MTRO) during primary TKA to achieve coronal balance. This patient population was matched 1:1 to another cohort of TKA patients by age, gender, and body mass index who did not require an MTRO. A radiographic evaluation was used to compare the 2 cohorts. RESULTS Preoperatively, the MTRO cohort was noted to have significantly increased varus tibiofemoral (86.12° vs 93.43°), tibial articular surface (85.79° vs 87.54°), and medial tibial articular surface angles (75.22° vs 85.34°) compared to the control cohort. The MTRO cohort had 3.13 mm of medial tibial offset and 9.06 mm of lateral joint space opening and the control cohort had 0.09 mm and 4.07 mm, respectively. The medial tibial articular surface angle and lateral joint space widening were statistically associated with the MTRO cohort. The final tibiofemoral angle in the MTRO cohort was 92.43° and was 93.40° in the control cohort. CONCLUSION The MTRO cohort was noted to have several preoperative radiographic parameters that were significantly different than the control cohort. However, the medial tibial articular surface angle and lateral joint space widening were the only radiographic parameters that were statistically associated with requiring an MTRO.

Removing a well-fixed femoral sleeve during revision total knee arthroplasty

The following surgical technique describes a case of a 51-year-old man with severe juvenile rheumatoid arthritis that required a 2-stage revision of an infected revision total knee implant. The patient had previously been implanted with a revision rotating platform, constrained condylar device which gained excellent fixation through the use of diaphyseal-engaging stems, and a well-ingrown, fully porous-coated femoral metaphyseal sleeve. To avoid intraoperative complications while removing the femoral sleeve, a novel technique for femoral sleeve extraction was used. Using this technique, the femoral sleeve was successfully removed without intraoperative fracture or substantial bone loss.

10 Avoiding Wound Complications in Total Knee Replacement

Wound complications are difficult problems following a total knee replacement and are best prevented. Careful preoperative evaluation of patients can identify patients with an increased risk of wound complications. Optimizing management of diabetes mellitus, tobacco use, and obesity potentially can decrease risk. Meticulous surgical technique, proper incision selection, and careful hemostasis maximize wound healing. Prolonged wound drainage and skin edge necrosis often necessitate operative intervention. Complex cases may require plastic surgery consultation and soft-tissue transfer procedures.

Management of Tibial Bone Loss

Severe tibial bone loss is one of the most challenging aspects in revision total knee arthroplasty (TKA). Bone loss can be the result of (1) aseptic failure with component loosening, subsidence, osteolysis, and fracture, (2) septic failure with bone resorption and osteolysis, and (3) iatrogenic bone loss following component removal. Accurate assessment of the severity of the tibial bone loss is necessary, especially in the proximal metaphysis, since it impacts tibial component position and fixation. Despite several classification systems, the radiographic evaluation of the bone defects is often difficult and underestimated [1]. The final determination of tibial bone loss is made at the time of surgery. The most useful classification system is the Anderson Orthopaedic Research Institute (AORI) classification that describes the severity of the tibial bone loss based upon the integrity of the metaphysis and whether one or both plateaus are involved [2].

Management of Severe Femoral Bone Loss

Severe femoral bone loss can be the result of aseptic or septic loosening, periprosthetic fracture, or iatrogenic bone loss secondary to the implant removal. The Anderson Orthopaedic Research Institute (AORI) classification has become a standard. The F1 defects can almost be ignored and require simple autografting or cement fill. The F2 defects are slightly more complicated with some associated cortical loss and require defect reconstruction and intramedullary stems. The F3 defects involve bone loss and soft tissue compromise and require defect reconstruction and ligamentous support from the prosthetic device itself.

5 Measured Resection and Gap Balancing Technique in TKR

Creating balanced flexion and extension gaps is a crucial technical goal in TKR. Both measured resection and gap balancing techniques are currently used to establish femoral rotation and a rectangular flexion gap. Current data suggests use of the measured resection technique often results in flexion gap asymmetry and an increased incidence of femoral condylar lift-off. Due to the bony deformities often encountered in knee osteoarthritis, reproducibly identifying important bone landmarks can be limited. The gap balancing technique is independent of bony anatomy and, in the authors’ opinion, can be used to provide more reproducible flexion gap stability.