Anatomic tibial component design can increase tibial coverage and rotational alignment accuracy: a comparison of six contemporary designs.

PURPOSE: The aim of this study was to comprehensively evaluate contemporary tibial component designs against global tibial anatomy. We hypothesized that anatomically designed tibial components offer increased morphological fit to the resected proximal tibia with increased alignment accuracy compared to symmetric and asymmetric designs. METHODS: Using a multi-ethnic bone dataset, six contemporary tibial component designs were investigated, including anatomic, asymmetric, and symmetric design types. Investigations included (1) measurement of component conformity to the resected tibia using a comprehensive set of size and shape metrics; (2) assessment of component coverage on the resected tibia while ensuring clinically acceptable levels of rotation and overhang; and (3) evaluation of the incidence and severity of component downsizing due to adherence to rotational alignment and overhang requirements, and the associated compromise in tibial coverage. Differences in coverage were statistically compared across designs and ethnicities, as well as between placements with or without enforcement of proper rotational alignment. RESULTS: Compared to non-anatomic designs investigated, the anatomic design exhibited better conformity to resected tibial morphology in size and shape, higher tibial coverage (92% compared to 85-87%), more cortical support (posteromedial region), lower incidence of downsizing (3% compared to 39-60%), and less compromise of tibial coverage (0.5% compared to 4-6%) when enforcing proper rotational alignment. CONCLUSIONS: The anatomic design demonstrated meaningful increase in tibial coverage with accurate rotational alignment compared to symmetric and asymmetric designs, suggesting its potential for less intra-operative compromises and improved performance. LEVEL OF EVIDENCE: III.

Dilemma of high rate of conversion from knee arthroscopy to total knee arthroplasty.

We tried to reduce our rate of conversion from index knee arthroscopy to total knee arthroplasty (TKA) for degenerative pathology (primarily meniscal) in the setting of coexisting arthritis in patients 50 years or older. We hypothesized that, by using a 2-surgeon independent evaluation method, we could reduce the rate to less than 10% by 3-year follow-up. Forty-two consecutive patients were initially evaluated by the knee replacement surgeon to determine if they were TKA candidates. They were then independently evaluated by another surgeon regarding the need for TKA and the possibility of arthroscopic debridement. The data showed a tendency: The under-10% target rate was nearly reached in patients younger than 65 years (12%; 2/17) but not in patients older than 65 years (36%; 9/25). The overall rate of conversion to TKA was 26%. The 2 main groups (arthroscopy only, arthroscopy-plus-TKA) did not differ in all measured characteristics. Failure of our method to achieve better outcomes demonstrates that conventional criteria are poor in predicting which patients with meniscal pathology, which is believed to be relatively more symptomatic than coexisting arthritis, should avoid arthroscopy and go straight to TKA.

Effect of total knee prosthesis design on patellar tracking and need for lateral retinacular release.

Intraoperative lateral retinacular release (LRR) during primary total knee arthroplasty (TKA) is discouraged, except when LRR is necessary to centralize patellofemoral tracking. This study compares the LRR rates in four designs of total knee implants and correlates how changes in prosthesis design affect LRR rates. 2881 primary TKAs performed by one surgeon using a single surgical technique were reviewed. After controlling for all variables, LRR rates dropped from 71.6% to 19.5% to 9.7% to 2.7% with each design change (P<.0001). Differences in varus/valgus alignment and male/female proportions were compared in each group and the differences did not correlate with LRR rates. This study concludes that changes and improvements in knee implant designs play a significant role in decreasing lateral retinacular release rates in TKA.

In vivo determination of total knee arthroplasty kinematics: a multicenter analysis of an asymmetrical posterior cruciate retaining total knee arthroplasty.

The objective of this study was to determine if consistent posterior femoral rollback of an asymmetrical posterior cruciate retaining (PCR) total knee arthroplasty was mostly influenced by the implant design, surgical technique, or presence of a well-functioning posterior cruciate ligament (PCL). Three-dimensional femorotibial kinematics was determined for 80 subjects implanted by 3 surgeons, and each subject was evaluated under fluoroscopic surveillance during a deep knee bend. All subjects in this present study having an intact PCL had a well-functioning PCR knee and experienced normal kinematic patterns, although less in magnitude than the normal knee. In addition, a surprising finding was that, on average, subjects without a PCL still achieved posterior femoral rollback from full extension to maximum knee flexion. The findings in this study revealed that implant design did contribute to the normal kinematics demonstrated by subjects having this asymmetrical PCR total knee arthroplasty.

Tibial component fixation in total knee arthroplasty: a comparison of pegged and stemmed designs.

This study compares midterm radiographic, functional, and quality-of-life outcomes in patients receiving a cemented tibial component that has either a short intramedullary stem or one that has a pegged tibial component. A cohort of 181 patients received 225 NexGen cruciate-retaining implants (84 stemmed, 141 pegged) during total knee arthroplasty, with annual follow-up examinations for up to 7 years. Both types of tibial components were associated with excellent radiographic and clinical results with no radiographic evidence of implant loosening or osteolysis. Clinical outcomes included improvement in joint function and patient function, as well as quality of life. Survival analysis showed 98% survival at 7 years with both implants. Pegged tibial components offered comparable midterm radiographic, functional, and quality-of-life results to stemmed components.

The orthopedist as clinical densitometrist: cost- and time-effectiveness.

We tested the hypothesis that an orthopedic surgeon and his or her staff can efficiently and economically provide a bone densitometry service. This hypothesis reflects a philosophy that orthopedists should take a more active role in identifying patients at risk for osteoporosis. We evaluated the cost- and time-effectiveness of an orthopedic surgeon and his medical assistant in completing reports and related correspondence for dual-energy x-ray absorptiometry scans conducted in an orthopedic subspecialty clinic. Cost analysis showed that completing 14 or 15 reports per month was required to break even and that completing up to 40 reports per month was a highly efficient and economic use of the surgeon's time.

Cruciate-retaining total knee arthroplasty at 5 to 7 years followup.

UNLABELLED: Cruciate-retaining total knee implants may improve postoperative function in total knee arthroplasty, but whether patients experience good restoration of kinematics, undue wear, or increased revision rates is debatable. I evaluated clinical results, radiographs, and survival rates of the NexGen posterior cruciate-retaining implant at 5-7 years followup in 251 knees (198 patients) in a prospective, consecutive total knee replacement series done from 1996-1997. A consistent improvement in knee scores and range of motion was observed from preoperative evaluation through 5 years followup. Alignment remained constant and knee stability did not deteriorate. Knee Society scores were good or excellent for 90% of patients. The average range of motion was 123 degrees, and 73% of patients achieved a mean range of motion of 116 degrees -130 degrees. Mean physical quality of life measures improved from preoperative evaluation to the last followup. There were no complete or progressive radiolucencies. Four screw radiolucencies had progressive increases in diameter. Survival of the implant at 7 years was more than 98%. The NexGen posterior cruciate-retaining implant provided satisfactory kinematic and clinical results with no substantive polyethylene wear. LEVEL OF EVIDENCE: Therapeutic study, Level II-2 (poor-quality randomized controlled trial). See the Guidelines for Authors for a complete description of levels of evidence.

Minimally invasive outpatient total hip arthroplasty: a financial analysis.

UNLABELLED: Costs of outpatient total hip arthroplasties were compared with costs of a matched group of patients having inpatient total hip arthroplasties. Ten patients were in each group and had surgery by the same surgeon in the same hospital. The average hospital bill for the outpatients was $4000 less than for the inpatients. The total average charge including prehospital, intrahospital, and posthospital care for the outpatients was approximately $2500 less than for the inpatients. The total average reimbursement was $1155 less for the outpatients. Results of this pilot study show that outpatient total hip arthroplasty is financially advantageous. LEVEL OF EVIDENCE: Economic and decision analyses, Level IV (no sensitivity analyses). See the Guidelines for Authors for a complete description of levels of evidence.

Anterolateral mini-incision hip replacement surgery: a modified Watson-Jones approach.

Mini-incision total hip replacement seeks to eliminate some complications of traditional extensile exposure and also attempts to facilitate more rapid rehabilitation of patients after surgery. Different surgical approaches historically have been used to do hip replacement surgery. Anterior or anterolateral approaches have often been selected to decrease the risk of posterior dislocation. Traditional anterolateral approaches have divided the anterior portion of the gluteus medius and minimus and potentially jeopardized the superior gluteal nerve. These disadvantages have been associated with abductor weakness, prolonged limp and decreased patient satisfaction. To overcome these problems, a mini-incision approach was developed using the intermuscular plane between the gluteus medius and the tensor fascia lata. This intermuscular interval through a small incision provides good exposure for total hip replacement and preserves muscle integrity so that rehabilitation can be rapid and the posterior capsule remains intact so that posterior dislocation is less of an issue. The surgical technique for this new innovative approach is described in this article.

In vivo determination of posterior femoral rollback for subjects having a NexGen posterior cruciate-retaining total knee arthroplasty.

This study determines the in vivo kinematics during a deep-knee bend activity for subjects implanted with a posterior cruciate-retaining total knee arthroplasty having asymmetric geometries. Of 20 subjects, 19 experienced posterior femoral rollback (PFR) of the lateral condyle (average -3.9 mm), and 13 subjects experienced PFR of the medial condyle (average -3.1 mm). As a result of the lateral condyle rolling further posterior than the medial condyle, on average, subjects experienced 1.4 degrees of normal axial rotation. Of 20 subjects, 10 experienced normal axial rotation, whereas 10 experienced an opposite rotation pattern. Condylar lift-off occurred predominantly with the lateral condyle. Contrary to previous in vivo studies, the subjects in this study experienced consistent PFR of the posterior cruciate-retaining total knee arthroplasty. It can be hypothesized that having asymmetric femoral condyles may lead to PFR with increasing knee flexion.

Repair of transverse sternal nonunions using metal plates and autogenous bone graft.

Transverse sternal nonunion is a complication of sternal fracture or partial sternotomy, and requires surgical treatment. Three patients with repeated failure of standard sternal repair were treated with a technique using metal plates and autogenous bone graft, which resulted in bone union in all patients. Metal plating of the sternum, accompanied by autogenous bone graft, is an effective method of treating transverse sternal nonunion.