Michael B. Cross

Accelerometer-Based, Portable Navigation vs Imageless, Large-Console Computer-Assisted Navigation in Total Knee Arthroplasty: A Comparison of Radiographic Results

Computer-assisted surgery (CAS) systems improve alignment accuracy in total knee arthroplasty (TKA) but have not been widely implemented. Eighty knees underwent TKA using an accelerometer-based, portable navigation device (KneeAlign 2; OrthAlign Inc, Aliso Viejo, California), and the radiographic results were compared with 80 knees performed using a large-console, imageless CAS system (AchieveCAS; Smith and Nephew, Memphis, Tennessee). In the KneeAlign 2 cohort, 92.5% of patients had an alignment within 3° of a neutral mechanical axis (vs 86.3% with AchieveCAS, P < .01), 96.2% had a tibial component alignment within 2° of perpendicular to tibial mechanical axis (vs 97.5% with AchieveCAS, P = .8), and 94.9% had a femoral component alignment within 2° of perpendicular to the femoral mechanical axis (vs 92.5% with AchieveCAS, P < .01). The mean tourniquet time in the KneeAlign 2 cohort was 48.1 ± 10.2 minutes vs 54.1 ± 10.5 minutes in the AchieveCAS cohort (P < .01). Accelerometer-based, portable navigation is as accurate as large-console, imageless CAS systems in TKA.

Radiographic Analysis of a Hand-Held Surgical Navigation System for Tibial Resection in Total Knee Arthroplasty

Tibial intramedullary or extramedullary alignment guides have not been shown to be highly accurate in performing the tibial resection in total knee arthroplasty (TKA). Since May 2010, a total of 42 knees underwent a TKA using a hand-held, accelerometer-based surgical navigation system for performing the tibial resection (KneeAlign; OrthAlign Inc, Aliso Viejo, Calif). Postoperative standing anteroposterior hip-to-ankle and lateral knee-to-ankle radiographs demonstrated that 97.6% of the tibial components were placed within 90° ± 2° to the mechanical axis in the coronal plane, and 96.2% of the components were placed within 3° ± 2° to the mechanical axis in the sagittal plane. The KneeAlign greatly improves the accuracy of tibial component alignment in TKA.

Accelerometer-Based Computer Navigation for Performing the Distal Femoral Resection in Total Knee Arthroplasty

The use of intramedullary alignment guides for performing the distal femoral resection in total knee arthroplasty (TKA) have not been shown to be highly accurate. Forty-eight knees underwent a TKA using a portable, accelerometer-based surgical navigation system for performing the distal femoral resection (KneeAlign 2 system; OrthAlign, Inc, Aliso Viejo, Calif). Of the femoral components, 95.8% were placed within 90° ± 2° to the femoral mechanical axis in the coronal plane, and 93.8% of the TKAs had an overall lower extremity alignment within 3° of neutral to the mechanical axis, based on postoperative, standing, hip-to-ankle radiographs. The KneeAlign 2 is highly accurate in positioning the femoral component in TKA, and accelerometer-based navigation is able to reliably determine the hip center of rotation and femoral mechanical axis.

Vascular anatomy of the patella: Implications for total knee arthroplasty surgical approaches

BACKGROUND Iatrogenic disruption of the patellar vascular supply has been identified as a possible contributing factor to the commonly reported patellofemoral complications following total knee arthroplasty (TKA). We performed an anatomic cadaveric study evaluating the extra-osseous vascular anatomy of the patella, and correlated our findings to routine TKA surgical dissection to determine how to better preserve patellar vascularity. METHODS AND MATERIALS In twenty-one cadaveric knees arterial cannulas were placed proximally and distally to the patella. A polyurethane compound was then injected producing a visible arterial network. Specimens underwent gross dissection. RESULTS In all 21 specimens, the supreme genicular (SGA), medial/lateral superior genicular (MSGA/LSGA), medial/lateral inferior genicular and anterior tibial recurrent arteries communicate forming a peripatellar anastomotic ring supplying the intraosseous patellar system. Both the SGA (24%) and MSGA (76%) demonstrated dual medial ring contribution. Relating the arterial location to common TKA exposures suggested severe compromise of patellar vascularity. CONCLUSION The medial sided vessels seem to contribute more significantly to the peripatellar anastomotic ring when compared to the lateral sided vessels. Careful soft tissue management has the potential to preserve key vascular structures that could maintain the intraosseous vascular supply to the patella. Understanding the anatomic locations of major arterial systems around the knee joint can potentially help during hemostasis, and can minimize blood loss during TKA. CLINICAL RELEVANCE Recognition of major arterial systems around the knee joint has the potential to minimize iatrogenic disruption of the vascular supply and the complications that can follow (patella devascularization and blood lost).

Cadaveric analysis of an accelerometer-based portable navigation device for distal femoral cutting block alignment in total knee arthroplasty

Femoral intramedullary guides have been shown to be insufficiently accurate in creating a distal femoral resection perpendicular to the mechanical axis in total knee arthroplasty (TKA), as they make assumptions regarding the difference between the patients femoral mechanical and anatomical angles. The aim of this cadaveric study was to validate the accuracy of a portable accelerometer-based navigation device for alignment of the distal femoral cutting block in TKA. Twenty-nine trials were performed on five cadaveric specimens (hip-to-ankle), in which the distal femoral cutting block was placed using the KneeAlign 2™ navigation device. For each specimen, a preoperative “target” was assigned for varus/valgus and flexion/extension alignment of the cutting block. The actual alignment of each cutting block was then measured using the ORTHOsoft Computer Assisted Surgery (CAS) system. The mean absolute difference between the preoperative target and the alignment of the cutting block was 0.83 ± 0.60° for varus/valgus, and 0.83 ± 0.83° for flexion/extension. The KneeAlign 2™ navigation device can set and align the distal femoral resection guide with the same accuracy as a large-console CAS system, thus demonstrating that portable accelerometer-based navigation can be used reliably in total knee arthroplasty.

Erratum to: Clinical Results and Failure Mechanisms of a Nonmodular Constrained Knee Without Stem Extensions

[This corrects the article DOI: 10.1007/s11420-012-9277-9.].

Incision in the Quadriceps of >4 cm Delayed Recovery of Strength After Total Knee Replacement.

Chareancholvanich K, Pornrattanamaneewong C. Does the Length of Incision in the Quadriceps Affect the Recovery of Strength After Total Knee Replacement? A Prospective Randomised Clinical Trial. Bone Joint J. 2014 Jul;96-B(7):902-6. ### Question: In patients having total knee replacement, does the length of incision in the quadriceps affect the time to recover the preoperative quadriceps strength? ### Design: Randomized (unclear allocation concealment), blinded (patients and outcome assessor), controlled trial with 12 months of follow-up. ### Setting: A university hospital in Bangkok, Thailand. ### Patients: 60 patients (mean age, 68 years; 87% women) who were undergoing total knee replacement for late-stage primary osteoarthritis. Exclusion criteria were varus or valgus deformity of >20°, flexion contracture of >30°, range of flexion of <60°, or previous knee surgery. All patients completed follow-up. ### Intervention: Patients were allocated to quadriceps incisions measuring 2 cm (n = 20), 4 cm (n = 20), and 6 cm (n = 20) in length. Total knee replacement was performed by 1 surgeon with the patient under regional anesthesia with use of a tourniquet at 350 mm Hg of pressure. The quadriceps incision …