Effects of degeneration on the compressive and tensile properties of human meniscus.

Healthy menisci function within the joint to prevent the underlying articular cartilage from excessive loads. Understanding how mechanical properties of menisci change with degeneration can drive future therapeutic studies to prevent this degeneration. Thus, the goal of this study was to characterize both compressive and tensile moduli of human menisci with varying degrees of gross damage due to osteoarthritis (OA). Twenty four paired menisci were collected from total knee joint replacement patients and the menisci were graded on a scale from 0-4 according to level of gross meniscal degeneration with 0=normal and 4=full tissue maceration. Each meniscus was then sectioned into anterior and posterior regions and subjected to indentation relaxation tests. Samples were sliced into 1mm thick strips, made into dumbbells using a custom punch, and pulled to failure. Significant decreases in instantaneous compressive modulus were seen in the lateral posterior region between grades 0 and 1 (36% decrease) and in the medial anterior regions between grades 1 and 2 (67% decrease) and 1 and 3 (72% decrease). Changes in equilibrium modulus where seen in the lateral anterior region between grades 1 and 2 (35% decrease), lateral posterior region between grades 0-2 (41% decrease), and medial anterior regions between grades 1 and 2 (59% decrease), 1 and 3 (67% decrease), 2 and 4 (54% decrease), and 3 and 4 (42% decrease). No significant changes were observed in tensile modulus across all regions and degenerative grades. The results of this study demonstrate the compressive moduli are affected even in early stages of gross degeneration, and continue to decrease with increased deterioration. However, osteoarthritic menisci retain a tensile modulus similar to that of previously reported healthy menisci. This study highlights progressive changes in meniscal mechanical compressive integrity as level of gross tissue degradation increases, and thus, early interventions should focus on restoring or preserving compressive integrity.

In Vivo Performance of Moderately Crosslinked, Thermally Treated Polyethylene in a Prospective Randomized Controlled Primary Total Knee Arthroplasty Trial.

Cross-linked bearings have been developed for use in total knee arthroplasty that exhibit improved wear properties, but at the expense of a decrease in mechanical strength of the cross-linked material. Adoption has been slow due to fears of mechanical failure secondary to this alteration in mechanical properties. This prospective, randomized study compared mid-term survivorship, clinical and radiographic results of a conventional polyethylene (GVF) to a cross-linked polyethylene (XLK) in total knee prostheses of the same design. At minimum 5-year follow-up there was no difference in survivorship, clinical performance or radiographic findings between the groups. There were no revisions for polyethylene wear, osteolysis or tibial insert dissociation. Most importantly, there were no revisions for mechanical failure or fracture of the polyethylene bearing in either group.

Evaluation of total knee arthroplasty performed with and without computer navigation: a bilateral total knee arthroplasty study.

Sequential bilateral total knee arthroplasty performed on 54 patients utilizing navigation (CAS-TKA) in one knee and traditional instrumentation (T-TKA) in the contralateral knee was reviewed at a mean follow-up duration of 2.5years. There were no differences with regard to KSS, ROM, postoperative anatomic alignment, mechanical axis, or tibial angle. There was a statistically significant decrease in outliers for the CAS-TKA group with respect to anatomic alignment (3.7% vs. 17.0%, P=0.024), mechanical axis (6.1 vs. 20.4%, P=0.037) and tibial component alignment (0% vs. 7.5%, P=0.042). There is no apparent benefit of CAS-TKA with regards to KSS, ROM, or alignment in the hands of fellowship-trained total joint specialists. The clinical relevance of reduced outliers in the CAS-TKA group is unknown with the current follow-up interval.

Large-diameter modular metal-on-metal total hip arthroplasty: incidence of revision for adverse reaction to metallic debris.

Large-diameter modular metal-on-metal (MOM) total hip arthroplasty (THA) may offer reduction in wear debris and improved stability. Four studies are summarized here that used a large-diameter modular MOM system. A total of 1076 THAs were performed. This article presents data from 779 of these THAs with minimum 2-year follow-up (mean, 4.2 years) or revision since index THA (21 hips, with 1 more pending). Overall survivorship at 2 years was 98.6%; at 5 years, it was 97.0%. Seven revisions for an adverse reaction to metallic debris (ARMED), and 1 additional pending revision for ARMED, showed marked variability in presenting symptoms and intraoperative and postoperative findings. Data show good clinical performance of the modular MOM system, but suggest that surgeons must be diligent in monitoring MOM THA patients and aggressive in diagnosing and revising patients with a potential ARMED.

Minimum 5-year results of modular metal-on-metal total hip arthroplasty.

This study reports minimum 5-year results of 95 hips implanted with a Pinnacle (DePuy, Warsaw, Ind) modular metal-on-metal acetabular prosthesis. Clinical scores such as the Harris Hip and Western Ontario and McMaster Universities Arthritis Index revealed excellent clinical outcomes at mean 6-year follow-up. With the use of large-diameter femoral heads, dislocation was rare, occurring in only 1 hip. Moreover, no acetabular and only 3 femoral osteolytic lesions were detected. Kaplan-Meier survivorship at 7 years after arthroplasty was 97.8% for the total hip arthroplasty construct and 100% for the acetabular shell. No unexplained pain or other complication attributable to wear debris or the metal-on-metal articulation was observed. These findings indicate that total hip arthroplasty with this specific modular metal-on-metal bearing performed well in a high-demand population at midterm follow-up.

The incidence of femoral component version change in primary THA using the S-ROM femoral component.

Although use of modular femoral components in revision total hip arthroplasty (THA) is widely accepted, many still question the need for modular versatility in primary THA. This study examined a large cohort of primary THA patients implanted with a modular S-ROM femoral component (DePuy Orthopaedics, Warsaw, Indiana) to determine the percentage of hips in which the surgeon changed version of the femoral component to increase the intraoperative stability of the THA construct and/or to maximize hip range of motion without impingement.In a group of 1000 routine, primary THAs, femoral component version was changed in 479 hips (47.9%). This change in rotational position of the femoral stem ranged from 60° retroversion with respect to the position of the sleeve to 80° of anteversion with respect to the sleeve. Ten hips (1%) experienced dislocation within the first 3 postoperative months. There was no difference in the dislocation rate between those patients in which femoral component version was changed versus those in which version was not changed. Statistical analysis showed no correlation between the likelihood of changing stem version and any of the following clinical variables: patient age, sex, diagnosis, or surgeon.The high percentage of straightforward primary THAs in which it was deemed beneficial to change version of the stem combined with the lack of correlation between femoral version change and clinical variables leads us to conclude that the routine use of a stem that allows variable version may be advantageous when compared to a nonmodular stem, as it is not possible to preoperatively determine when changing version will be required.

Unrecognized acetabular component rotation with formation of a pseudoarticulation after total hip arthroplasty.

We report an unusual case of an 82-year-old woman who presented with bilateral knee pain and advanced tibial-femoral and patellofemoral arthrosis. A preoperative total lower extremity film revealed an unrecognized, asymptomatic, dislocated right total hip arthroplasty with a rotated acetabular component that likely occurred 12 years earlier. The dislocated prosthetic femoral head appeared to be articulating with a pseudoacetabulum that had formed superiorly and laterally to the acetabular cup. The patient was unaware of any incident where she noticed an acute change after her hip arthroplasty surgery. We believed the patient to have a chronically dislocated hip that was pain free and quite functional for many years, an unusual condition that has not been reported previously in the literature.