Major Shortening of the Patellar Tendon During Septic Two-Stage Knee Arthroplasty Revision Using Static Spacers.

BACKGROUND: Two-stage septic revision knee arthroplasty (TKA) often results in inferior functional outcome after reimplantation, which might be due to impairments of the extensor mechanism. The aim of the current study was to elucidate possible alterations in extensor mechanisms during septic two-stage revision of TKA treated with a static spacer. METHODS: This retrospective study included 87 patients (42 women, 45 men, age 64.5 ± 10.5; range, 29-85 years) undergoing septic two-stage TKA revision using a static spacer. The modified Insall Salvati ratio (mISR) was calculated via calibrated true lateral radiographs by two independent orthopedic surgeons before TKA explantation (G0), 6-8 days after TKA removal (G1), one day before TKA reimplantation (G2) and 6-8 days after TKA reimplantation (G3). Age, sex, body mass index (BMI), index C-reactive protein level, and number of previous surgeries were evaluated to identify the possible correlations. RESULTS: Overall, mISR significantly decreased within the first 6 days after index surgery from 1.71 ± 0.41 to 1.63 ± 0.41 (G0 versus G1, P < .001) and showed a further decline within the next 6 weeks to 1.54 ± 0.39 (G1 versus G2, P = .002). Conversely, mISR increased after reimplantation of TKA to 1.6 ± 0.43 (G3 versus G2, P = .08), though it did not regain preoperative baseline levels (G0 versus G3, P < .001). The subgroup with mISR decrease ≥10% experienced patellar tendon shortening of 16% between G0 and G1, 19% between G0 and G2 and up to 20% between G0 and G3. There were weak correlations concerning age (r = -0.240, P = .038), preoperative C-reactive protein level (r = 0.239, P = .04) and patellar tendon shortening. Intraclass correlation coefficient (ICC)was 0.88 concerning radiographic measurement. CONCLUSION: Septic two-stage TKA revision using static spacers leads to irreversible alterations of the extensor mechanism, specifically a major shortening of the patellar tendon, in one out of 3 patients. LEVEL OF EVIDENCE: II.

[Nerve Injuries in Hip and Knee Arthroplasty - Risk Factors, Diagnostic and Therapeutic Approaches]. / Iatrogene Nervenläsionen in der Hüft- und Knieendoprothetik.

Iatrogenic nerve injuries are rare complications of total hip and knee arthroplasty, which may cause chronic pain and loss of function, severely affecting the patient's daily activities and quality of life. Nerves "at risk" include the sciatic nerve, the femoral nerve, the lateral femoral cutaneous nerve and the superior gluteal nerve during total hip arthroplasty, and the infrapatellar branch of the saphenous nerve as well as the peroneal nerve during total knee arthroplasty. Multiple procedure-related and patient-related factors have been identified to modify the risk of nerve injury in the course of lower limb joint replacement surgery. These include the surgeon's skills, the surgical approach, the type of implant fixation, the intraoperative positioning of the patient, as well as pre-existing scars, the patient's sex, age and comorbidities. Diagnostic and therapeutic approaches should be based on the aetiology of the lesion: iatrogenic nerve lesions can result from direct (compression or transection) and/or indirect (traction, ischemia) trauma. The majority of nerve injuries encountered in hip or knee arthroplasty has been referred to as "minor" nerve lesions, which generally respond very well to non-operative treatment. "Major" nerve lesions, such as complete motor nerve transection, may result in lifelong impairment. Any perioperatively encountered neurological deficit requires a meticulous diagnostic work-up and an individually tailored treatment strategy, respecting aetiology and anatomic site of the nerve lesion as well as the individual patient's needs and comorbidities.

[Importance of the tibial slope in knee arthroplasty]. / Bedeutung des tibialen Slopes in der Knieendoprothetik.

Notwithstanding the contributions of soft tissue restraints on postoperative kinematics and long-term survival after total knee arthroplasty (TKA), there is an emerging consensus that the underlying anatomy, especially the posterior inclination of the tibial plateau in the sagittal plane (tibial slope), might just have a comparable impact. However, this has not been fully elucidated as yet. Therefore, a thorough literature search, analysis and presentation of current scientific data was conducted. The tibial slope has been shown to relate linearly to the postoperative range of motion and function of the extensor mechanism. Furthermore, it impacts wear of the tibial insert and loosening, as well as instability of the TKA. As no consensus has been reached on the ideal tibial slope, recommendations range from 0° to 10°. Notably, more recent studies favor reconstructing the native, preoperative tibial slope, and the majority of authors advocate that knowledge of this is crucial for optimal TKA surgery.