B. Lanting

Correlation of Corrosion and Biomechanics in the Retrieval of a Single Modular Neck Total Hip Arthroplasty Design: Modular Neck Total Hip Arthroplasty System

Increased modularity of total hip arthroplasty components has occurred, with theoretical advantages and disadvantages. Recent literature indicates the potential for elevated revision rates of modular neck systems and the potential for local pseudotumor and metallosis formation at the modular neck/stem site. Retrieval analysis of one modular neck implant design including SEM (SCANNING ELECTRON MICROSCOPY) assessment was done and correlated with FEA (finite element analysis) as well as clinical features of patient demographics, implant and laboratory analysis. Correlation of the consistent corrosion locations to FEA indicates that the material and design features of this system may result in a biomechanical reason for failure. The stem aspect of the modular neck/stem junction may be at particular risk.

The relationship between constitutional alignment and varus osteoarthritis of the knee

AbstractPurposenThe role of neutral alignment in total knee arthroplasty (TKA) on short- and long-term outcomes has become controversial. Based on the concept of constitutional varus, it has been suggested that under-correction in TKA in a varus osteoarthritis (OA) population might lead to better clinical outcomes. However, it is still unknown what the relationship between constitutional varus and the development of end-stage OA is. The goal of this study was to analyse the contribution of constitutional varus in a medial OA population and to define a correlation between the constitutional alignment and end-stage varus OA.MethodsBased on full-length radiographs, corrected for the intra-articular deformity of the knee, of 315 patients with unilateral end-stage medial OA of the knee (Charnley type A), a correlation in the coronal plane was made between medial end-stage OA and the contralateral non-arthritic side.ResultsWith increasing varus alignment in the arthritic limb, the physiologic limb alignment also became more varus. The proportion of constitutional varus rose with increasing overall alignment and was found to be continuous for males. Constitutional varus was three times higher in men when the overall arthritic alignment was greater more than 6° varus.ConclusionConstitutional varus significantly contributes to varus osteoarthritis and was found to be higher than in the general population.Level of evidenceIII.

The effect of excision of the radial head and metallic radial head replacement on the tension in the interosseous membrane

We measured the tension in the interosseous membrane in six cadaveric forearms using an in vitro forearm testing system with the native radial head, after excision of the radial head and after metallic radial head replacement. The tension almost doubled after excision of the radial head during simulated rotation of the forearm (p = 0.007). There was no significant difference in tension in the interosseous membrane between the native and radial head replacement states (p = 0.09). Maximal tension occurred in neutral rotation with both the native and the replaced radial head, but in pronation if the radial head was excised. Under an increasing axial load and with the forearm in a fixed position, the rate of increase in tension in the interosseous membrane was greater when the radial head was excised than for the native radial head or replacement states (p = 0.02). As there was no difference in tension between the native and radial head replacement states, a radial head replacement should provide a normal healing environment for the interosseous membrane after injury or following its reconstruction. Load sharing between the radius and ulna becomes normal after radial head Replacement. As excision of the radial head significantly increased the tension in the interosseous membrane it may potentially lead to its attritional failure over time.

The Impact of Coronal Plane Alignment on Polyethylene Wear and Damage in Total Knee Arthroplasty: A Retrieval Study

BACKGROUNDnCoronal plane alignment is one of the contributing factors to polyethylene wear in total knee arthroplasty.nnnMETHODSnBased on 95 retrieved polyethylene inserts, wear and damage patterns were analyzed in relationship to the overall mechanical alignment and to the position of the tibial component.nnnRESULTSnA progression of wear was observed with progressively mechanical varus alignment. However, there was significantly more damage in the lateral compartment in the mild and moderate varus group compared to the valgus group. No difference in damage was seen between all groups for tibial component positioning in valgus or varus.nnnCONCLUSIONnProgressive wear was observed with progressively varus alignment with more damage at the lateral side. This observation is unique and might be explained by lateral condylar lift-off inducing impact and shear loading in the varus group.

Outpatient Total Hip Arthroplasty, Total Knee Arthroplasty, and Unicompartmental Knee Arthroplasty: A Systematic Review of the Literature.

Background:The demand for total hip arthroplasty (THA), total knee arthroplasty (TKA), and unicompartmental knee arthroplasty (UKA) is growing rapidly because of the proven success of these procedures and an increase in the aging population. However, resources are limited and health-care budgets are finite. Recently, a number of care providers have started performing these procedures on an outpatient basis, with the patients being discharged from the hospital on the day of surgery. The primary objective of this systematic review was to examine the evidence regarding the safety and feasibility of performing THA, TKA, or UKA on an outpatient basis. Methods:An electronic search of 3 online databases (Embase, MEDLINE, and HealthSTAR) was conducted to identify eligible studies. The reference lists of identified articles were then screened. All studies evaluating outcomes following outpatient THA, TKA, or UKA were included. Eligible articles that included a comparative group were assessed for methodological quality with use of the Cochrane Risk of Bias Assessment Tool for Non-Randomized Studies of Interventions (ACROBAT-NRSI). Non-comparative studies were assessed for quality with use of the Effective Public Health Practice Project (EPHPP) Quality Assessment Instrument. Results:The electronic literature search yielded 805 articles. Following a review of the titles, abstracts and reference lists, 26 articles remained and were assessed for eligibility. Of those, 17 articles (≈79,500 patients) met the inclusion criteria and were included in the review. Although both quality-assessment tools showed that the majority of studies included in the review were of poor quality, there was no increase in readmission rates or perioperative complications among patients who underwent outpatient procedures. Studies assessing satisfaction illustrated a high level of satisfaction for the majority of patients. The average age of the patients in the THA studies ranged from 53.5 to 63 years. The TKA and UKA studies included an older population, with mean ages ranging from 55 to 68 years. The majority of the included studies included a larger percentage of males as compared with females. Of the 17 included studies, 4 were cohort studies with a control group and 13 were case series. All 4 cohort studies indicated that the complication rates and clinical outcomes were similar between the inpatient and outpatient groups. Furthermore, the 3 studies that involved an economic analysis indicated that outpatient arthroplasty is financially advantageous. Conclusions:In selected patients, outpatient THA, TKA, and UKA can be performed safely and effectively. The included studies lacked sufficient internal validity, sample size, methodological consistency, and standardization of protocols and outcomes. There is a need for high-quality prospective cohort and randomized trials to definitively assess the safety and effectiveness of outpatient THA, TKA, and UKA. Level of Evidence:Therapeutic Level IV. See Instructions for Authors for a complete description of levels of evidence.

Migration of a cemented fixed-bearing, polished titanium tibial baseplate (Genesis II) at ten years: a radiostereometric analysis

AIMSnThe purpose of the present study was to examine the long-term fixation of a cemented fixed-bearing polished titanium tibial baseplate (Genesis ll).nnnPATIENTS AND METHODSnPatients enrolled in a previous two-year prospective trial (n = 35) were recalled at ten years. Available patients (n = 15) underwent radiostereometric analysis (RSA) imaging in a supine position using a conventional RSA protocol. Migration of the tibial component in all planes was compared between initial and ten-year follow-up. Outcome scores including the Knee Society Score, Western Ontario and McMaster Universities Arthritis Index, 12-item Short Form Health Survey, Forgotten Joint Score, and University of California, Los Angeles Activity Score were recorded.nnnRESULTSnAt ten years, the mean migration of the tibial component was less than 0.1 mm and 0.1° in all planes relative to the post-operative RSA exam. Maximum total point movement increased with time (p = 0.002) from 0.23 mm (sd 0.18) at six weeks to 0.42 mm (sd 0.20) at ten years.nnnCONCLUSIONnThe low level of tibial baseplate migration found in the present study correlates to the low rate of revision for this implant as reported in individual studies and in joint replacement registries.nnnTAKE HOME MESSAGEnOverall, the implant was found to be well fixed at ten years, supporting its continued clinical use and the predictive power of RSA for determining long-term fixation of implants. Cite this article: Bone Joint J 2016;98-B:616-21.

The Impact of Wear and Lift-Off on Coronal Plane Alignment in TKA and Implications to Future Constrained Revision: A Retrieval Study

Current discussion exists whether to position a total knee arthroplasty (TKA) in slight undercorrection in varus osteoarthritis. The goal of this study was to analyse the effect of wear and lateral lift-off in primary TKA on coronal plane alignment and the implication to future constrained revision TKA. Seventy-six retrieved tibial inserts were analysed for the ratio of wear (RW), lateral lift-off and implications for future constrained revision surgery according to the coronal plane alignment. The RW significantly affects the coronal plane alignment in TKA. Progressive wear and lateral lift-off were seen with progressive varus alignment. However, there was no difference in constrained revision between mild varus and moderate varus aligned TKAs.

Effect of Soft Tissue Releases on Joint Space Opening in Total Knee Arthroplasty

BACKGROUNDnThe purpose of this study was to determine the gap achieved to the medial and lateral compartments following sectioning and release of the relevant soft tissues in preparation for a total knee arthroplasty.nnnMETHODSnA custom-designed knee tensioner allowed the application of forces to the medial and lateral compartments of 12 cadaveric knee specimens. Loads of 100 N and 200 N were applied to each compartment, and the resulting displacement was measured in the following conditions: (1) All soft tissues intact, (2) an arthrotomy, (3) anterior cruciate ligament (ACL) sectioned, (4) posterior cruciate ligament (PCL) sectioned, and (5) release of the anterior aspect of the deep medial collateral ligament (MCL) fibers. Tensions were applied for all conditions from 90° to 0° of knee flexion in 30° increments.nnnRESULTSnNo differences were found in medial or lateral displacement after the arthrotomy or releasing the ACL or PCL at either 100 N or 200 N. At the 100 N load application, there was a significant increase in gap width when the anterior portion of the deep MCL was released (7.49 mm) compared to the intact (5.28 mm) and arthrotomy (5.75 mm) conditions. With respect to the 200 N load application, there were statistically significant differences detected between the deep MCL fiber release (11.09 mm) and intact conditions (8.05 mm) and release of the deep MCL and arthrotomy conditions (8.77 mm).nnnCONCLUSIONnThe medial parapetellar arthrotomy, ACL and PCL sectioning did not result in medial or lateral displacement changes. The release of the anterior fibers of the deep MCL as part of the surgical exposure increased the medial gap magnitude.

Metal-on-Metal Compared With Metal-on-Polyethylene: The Effect on Trunnion Corrosion in Total Hip Arthroplasty

BACKGROUNDnTrunnion tribocorrosion in total hip arthroplasties is concerning, but retrieval studies often are subjective or lack comparison groups. Quantitative comparisons of clinically relevant implants are required. The purpose of this investigation was to evaluate material loss in metal-on-metal (MoM) and metal-on-polyethylene (MoP) total hip articulations while controlling for trunnion design and head size.nnnMETHODSnThe 166 retrieved femoral heads from 2 manufacturers were analyzed. Four cohorts based on head size, trunnion design, manufacturer, and articulation type (MoM vs MoP) were created. Corrosion was measured by a coordinate measurement machine, and material loss was assessed (MATLAB).nnnRESULTSnRetrieved femoral heads from MoP articulations had 5 times less trunnion material loss than MoM articulations, on average, for both manufacturers. There was no difference in material loss between large modular head (>40 mm) and 36-mm MoM hip trunnion. Implants with a material loss above the detectable limit demonstrated a correlation with time inxa0vivo only in MoP articulations.nnnCONCLUSIONnRetrieved femoral heads from MoP bearing couples had a lower magnitude of material loss than MoM couples, independent of head diameter. A time inxa0vivo effect was only seen in MoP bearings.

Outcomes of Surgical Management of Supracondylar Periprosthetic Femur Fractures.

BACKGROUNDnFracture location is an important consideration in managing supracondylar periprosthetic femur fractures. The outcomes of locked plating and intramedullary (IM) nail fixation were therefore compared based on fracture location, being above or at/below the total knee arthroplasty (TKA) flange.nnnMETHODSnFifty-seven patients were identified from surgical records as being treated for supracondylar periprosthetic femur fracture with either a locking plate (nxa0= 38) or IM nail (nxa0= 19). Based on fracture location, either above or at/below the TKA flange, both groups were assessed for time to full weight bearing, time to radiographic union, number of postoperative complications, subsequent surgery, transfusion requirements, as well as range of motion, pain, and instability at most recent follow-up. Radiographs were reviewed to assess fracture alignment with comparisons made immediately postoperative to most recent.nnnRESULTSnMean follow-up for IM nail and locking plate fixation was 13.9 and 15.6 months, respectively. There was no statistical difference between groups in the mean time to fully weight bear, the incidence of postoperative pain, range of motion, use of gait aids, time to full radiographic union, or the overall radiographic alignment of a healed fracture (P > .05). Comparison based on fracture location yielded similar outcomes. Nonunion was only demonstrated in the IM nail cohort, particularly for fractures below the TKA flange (nxa0= 2).nnnCONCLUSIONnThe use of either IM nail or locking plate fixation for supracondylar periprosthetic fractures provides comparable clinical outcomes. Caution is recommended in using IM nails for fractures below the flange where limited fixation may increase the risk of nonunion.