Clinical Outcomes Following the Use of Constrained Condylar Knees in Primary Total Knee Arthroplasty.

BACKGROUND: Certain clinical or adverse intraoperative situations require the use of increased constraint in primary total knee arthroplasty (TKA). These include significant angular deformities causing incompetent collateral ligaments, or inadvertent intraoperative injury to collateral structures as well as the inability to achieve a balanced flexion and extension gap. Clinical success has been described with the use of constrained condylar knee arthroplasty in the primary setting in these situations. Traditionally, increasing constraint has been in conjunction with intramedullary stems, referred to as stemmed constrained condylar knees (SCCK); however, some devices provide an intermediary option by increasing constraint without the use of stems, herein referred to as nonstemmed constrained condylar knees (NSCCK). The aim of this study was to compare the clinical outcomes of both these devices in primary TKA in terms of revision rates and change in outcome measures over the follow-up period. METHODS: Between 2007 and 2012, 85 SCCKs and 354 NSCCKs were identified in our institutional registry database performed in the primary TKA setting with minimum 2-year clinical outcome measure follow-up. Baseline demographic information, as well as Western Ontario and McMaster Universities Arthritis Index (WOMAC) and Lower Extremity Activity Scale (LEAS) were collected preoperatively at 2-year follow-up. Revision data were also collected. RESULTS: Both groups showed substantial improvement in WOMAC scores (pain, stiffness, and function), and LEAS at 2 years postoperatively compared with baseline, although the changes in scores were not statistically significant. One of 85 SCCKs (1.17%) was revised for infection, whereas 9 of 354 NSCCKs (2.54%) were revised (6 for mechanical complications, eg, loosening, 2 for periprosthetic fracture, and 1 for infection). CONCLUSION: Both cohorts demonstrated improvement in clinical outcome measures at 2-year follow-up. None of the SCCKs performed in the primary setting were revised for a mechanical complication. Although both groups had overall low revision rates, there was trend toward a higher revision rate with NSCCKs. Many of these were revised for component loosening. In summary, when necessary, constrained options in the primary TKA setting provide excellent clinical outcome at short-term follow-up. However, constrained constructs with stemmed fixation may provide more rigid fixation and be less susceptible to mechanical failure.

Comparison of Revision Rates of Non-modular Constrained Versus Posterior Stabilized Total Knee Arthroplasty: a Propensity Score Matched Cohort Study.

BACKGROUND: Attaining stability during total knee arthroplasty (TKA) is essential for a successful outcome. Although traditional constrained total knee prostheses have generally been used in conjunction with intramedullary stems, some devices have been widely used without the use of stems, referred to as non-modular constrained condylar total knee arthroplasty (NMCCK). QUESTIONS/PURPOSES: The aim of this study was to compare revisions rates after total knee replacement with a non-modular constrained condylar total knee (NMCCK) compared to a posterior-stabilized (PS) design. METHODS: Between 2007 and 2012, primary PS total knees were compared with NMCCK implants from the same manufacturer. Propensity score matching was performed, and implant survivorship was examined using a Cox proportional hazards model. The cohort consisted of 817 PS knees and 817 NMCCKs matched for patient demographics, surgeon volume, and pre-operative diagnosis. RESULTS: All cause revisions occurred in 11 of 817 (1.35%) in the PS group compared to 28 of 817 (3.43%) in the NMCCK group (p = 0.0168). Excluding revisions for infection and fracture, 8 of 817 (0.98%) PS knees required revision for mechanical failure compared to 18 of 817 (2.20%) NMCCK knees (p = 0.0193). CONCLUSIONS: While revisions rates in both cohorts were low, there was a significantly higher revision rate with NMCCKs. Given that cases requiring the use of NMCCK implants are likely more complex than those in which PS implants are used, our findings support the judicious use of NMCCK prostheses.

Hip dislocation increases roughness of oxidized zirconium femoral heads in total hip arthroplasty: an analysis of 59 retrievals.

The aims of this study were to assess damage on the surface of retrieved oxidized zirconium (OxZr) metal femoral heads, to measure surface roughness of scratches, and to evaluate the extent of surface effacement using scanning electron microscopy (SEM). Ceramic zirconia-toughened alumina heads were analyzed for comparison. OxZr femoral heads explanted for recurrent dislocation had the most severe damage (P<0.001). The median surface roughness of damaged OxZr femoral heads was 1.49µm, compared to 0.084µm for damaged ceramic heads and 0.052µm for undamaged OxZr (P<0.001). This may be of clinical concern because increased surface roughness has the potential to increase the wear of polyethylene liners articulating against these OxZr heads in THA.

Effect of immediate postoperative portable radiographs on reoperation in primary total knee arthroplasty.

Cost-containment strategies are of increasing importance in total knee arthroplasty (TKA). Obtaining immediate postoperative radiographs following primary TKA is common practice, but their usefulness is controversial. The goal of this study was to evaluate the effect of immediate postoperative radiographs on reoperation within 60 days, assess film quality, and determine the cost associated with these radiographs. Using a billing registry at the authors' institution, the number of TKAs performed from 2000 to 2011 was determined. Of those, the authors determined which had undergone reoperation within 60 days. They evaluated those who had immediate postoperative radiographs following their primary TKA, and determined those who had been reoperated on as a result of information obtained from these radiographs. Of 6603 patients who underwent primary TKA from 2000 to 2011, 136 (2%) underwent reoperation within the first 60 days. The causes leading to reoperation were arthrofibrosis, infection, wound-healing complications, and hematoma. Of the 136 who underwent reoperation, 76 had immediate postoperative radiographs. None of them underwent reoperation as a result of findings noted in the radiographs. Of the radiographs reviewed, only 43% were deemed adequate by predetermined criteria. The results of the current study demonstrate that these radiographs do not affect the decision for reoperations that occur within 60 days of the index procedure. Although there may be a benefit to immediate postoperative radiographs in selected clinical situations, the decision for routine use needs to be weighed in light of significant cost and limited clinical usefulness.

Missed locked posterior shoulder dislocation with a reverse Hill-Sachs lesion and subscapularis rupture.

We report the case of a patient who sustained a missed locked posterior shoulder dislocation with a sizable anterior impression fracture and a concomitant acute rupture of the subscapularis tendon. Despite compromise of the tendon, a transfer of the lesser tuberosity into the humeral head defect along with suture anchor repair of the subscapularis was performed. Within 6 months, the patient regained near complete function of his shoulder with no episodes of instability. To our knowledge, this is the first reported case of an acute subscapularis rupture associated with a posterior shoulder dislocation and anterior humeral impression fracture, treated with the modified McLaughlin procedure and tendon repair with an excellent clinical result.

Kinematic evaluation of the step-up exercise in anterior cruciate ligament deficiency.

BACKGROUND: Step-up exercise is one of the most commonly utilized exercises during rehabilitation of patients after both anterior cruciate ligament (ACL) injury and reconstruction. Currently, insurance providers increasingly required a trial of intensified rehabilitation before surgical reconstruction is attempted. The purpose of this study was to investigate whether this "safe" rehabilitation exercise in the setting of ACL deficiency can cause altered knee kinematics. METHODS: Thirty patients with unilateral ACL rupture were recruited for this study. The mean time from injury was 3.3 months. Tibiofemoral kinematics were determined during a step-up exercise using a combination of magnetic resonance imaging (MRI), dual fluoroscopy and advanced computer modeling. FINDINGS: The ACL-injured knee displayed an average 5° greater external tibial rotation than the uninjured knee (P<0.05), during the last 30% of step-up. The ACL-injured knee also demonstrated on average 2.5 mm greater anterior tibial shift during the last 40% of stance phase (P<0.01). In addition, during the last 30% of stance the tibia of the ACL-deficient knee tended to shift more medially (~1 mm) as the knee approached full extension (P<0.01). INTERPRETATION: The data confirmed the initial hypothesis as it was found that ACL deficient knees demonstrated significantly increased anterior tibial translation, medial tibial translation and external tibial rotation toward the end of the step-up as the knee approached full extension. Intensive rehabilitation utilizing the step-up exercise in the setting of ACL deficiency can potentially introduce repetitive microtrauma by way of altered kinematics.