Effect of bone density and cement morphology on biomechanical stability of tibial unicompartmental knee arthroplasty

BackgroundUnicompartmental knee arthroplasty (UKA) offers good long-term survivorship and superior kinematics and function compared with total knee arthroplasty (TKA). However, revision rates are higher with aseptic loosening representing a major cause. Biomechanical stability depends on cement penetration. The goal of this study was to analyze the influence of cement morphology and bone density on primary stability of tibial UKA under physiological loading conditions in human tibiae.MethodsThirty-six tibial trays were implanted in fresh-frozen human cadaver knees and tested for primary stability using dynamic compression–shear testing. Prior to implantation, bone density had been quantified for all 18 tibiae. Postoperatively, cement penetration has been assessed on frontal cuts based on eight predefined parameters. The influence of bone density and cement morphology on biomechanical stability was determined using correlation and linear regression analysis.ResultsMean failure load was 2691 ± 832.9 N, mean total cement thickness was 2.04 ± 0.37 mm, mean cement penetration was 1.54 ± 0.33 mm and mean trabecular bone mineral density (BMD) was 107.1 ± 29.3 mg/ml. There was no significant correlation between failure load and cement morphology (P > .05). Failure load was significantly positive correlated with trabecular BMD (r = 0.843; P < .0001) and cortical BMD (r = 0.432; P = .0136).ConclusionsSimulating physiological loading conditions, the failure load of tibial UKA is linearly dependent on the trabecular BMD. The observed parameters of cementation morphology seem capable of preventing failure at the bone–cement interface before inherent bone stability is reached. Further research is required to assess the usefulness of a preoperative assessment of bone quality for patient selection in UKA.     

Periprosthetic bone mineral density changes after unicondylar knee arthroplasty

BackgroundUnicompartmental knee arthroplasty (UKA) has received renewed interest in the last decade. UKA involves minor injury to soft tissues, limited removal of bone and delicate preservation of knee anatomy and geometry. In theory, UKA provides an opportunity to restore post-surgical knee kinematics to near normal.HypothesisUKA leaves patellofemoral joint free to meet high mechanical forces with no stress-shielding and therefore might preserve bone mineral density (BMD).Patients and methodsWe studied 21 patients with osteoarthritis(OA), who had received medial compartment UKA at Kuopio University Hospital between October 1997 and September 2000. BMD was measured by dual-energy X-ray absorptiometry (DEXA), at baseline (within a week after surgery) and at intervals until 7 years.ResultsDEXA results were reproducible. The highest rate of periprosthetic bone loss occurred during the first 3 months after UKA. The average loss in BMD was 4.4% (p = 0.039) in the femoral diaphysis and it ranged from 11.2% (p < 0.001) to 11.9% (p = 0.002) in the distal femoral metaphysis; however, BMD changes in these regions, from 2 years to 7 years, were nonsignificant. At the 1-year follow-up, the BMD of the medial tibial metaphysis had increased by 8.9% (p = 0.02), whereas those in the lateral tibial metaphysial (–2.4%) and diaphysial regions (–2.0%) did not change significantly.InterpretationsUKA did not preserve periprosthetic BMD in the distal femoral metaphysis, whereas BMD changes in the tibial metaphysis were minor, consistent with a mechanical balance between the medial and lateral tibial compartments.Level of Evidence 2bProspective case control study.     

Medial peg position of cementless porous tantalum tibial component affects bone mineral density around the prosthesis after total knee arthroplasty: 2-year follow-up study

BackgroundUse of a porous tantalum tibial component for total knee arthroplasty (TKA) was reported to have beneficial effects on periprosthetic bone mineral density (BMD). In some cases, hexagonal peg is placed close to or in contact with the tibial cortex, which may result in stress-shielding around the peg. However, no studies have analyzed the relationship between peg position and BMD. The aim of this study was to compare the peg position and BMD around the peg in a porous tantalum tibial component after TKA.MethodsTwenty-seven patients (27 knees) who underwent primary TKA with a cementless porous tantalum tibial component were investigated. BMD was measured by dual-energy X-ray absorptiometry for 2 years after the operation. The distance between the peg and the tibial cortex (peg distance) was measured on the medial and lateral sides.ResultsBMD was decreased in the medial region after the operation (p < 0.01). Relative change in BMD was lower in the medial region than in the central and lateral regions (p < 0.01). Multiple regression analysis showed that medial peg distance was negatively correlated with relative change of BMD in the medial part of the tibia (p = 0.04, R = 0.402).ConclusionsThe medial peg position affected the postoperative relative change of BMD in the medial part of the tibia, but did not affect the longevity of the implant. As the tibial medial peg became closer to the medial tibial cortex, the BMD loss became larger in the medial part of the tibia at 2 years postoperatively.     

Tibial metaphyseal sleeves in primary total knee arthroplasty following high tibial osteotomy and tibial plateau fracture; preliminary mid-term survival and outcome

BackgroundPrevious high tibial osteotomy (HTO), and tibial plateau fractures (TPF) may cause problems in subsequent total knee arthroplasty (TKA) due to altered metaphyseal bone structure. Higher rates of loosening of the tibial component have been described.In post-HTO and TPF cases, a more durable fixation could be achieved by tibial sleeves. This study investigates the preliminary short-to-midterm clinical and radiographic results in a cohort of these cases.MethodsA cohort of 28 patients was selected, 11 following HTO, and 17 following TPF. Standard clinical and radiologic follow-up was performed at 6 weeks, and one and two years. Revision with removal of primary prosthesis for any reason was the primary outcome. Patient reported pre- and postoperative pain, satisfaction and general health scores were collected at one and two years. Postoperative radiographs were analyzed for radiolucent lines.ResultsThere were no cases of aseptic loosening. Survival for all reasons was 96.4% (CI 77.2%–99.5%). One progressive radiolucent line was seen. Numerical rating scale (NRS) for pain with and without weightbearing at 2-year follow-up improved from 8 to 3 and from 5 to 2 points respectively. Overall general health scores improved with a median of 70 at ≥ 2 years, compared to 63 pre-operatively.ConclusionWith no revision for aseptic loosening the use of tibial sleeves in primary TKA seems a safe and reliable method for fixation of the tibial component in metaphyseal bone with altered bone structure at short and mid-term follow-up.Level of evidence: Level IV, cohort study.     

Less polyethylene wear in monobloc compared to modular ultra-high-molecular-weight-polyethylene inlays in hybrid total knee arthroplasty: A 5-year randomized radiostereometry study

BackgroundA modular polyethylene (PE) inlay in total knee arthroplasty (TKA) may wear on both sides. PE particles may induce osteolysis, which can lead to implant loosening. The aim of this study was to determine if PE wear in monobloc TKA differs from that of modular TKA at 60-month follow-up.Patients and methodsIn a prospective, patient-blinded trial, 50 patients were randomized to hybrid TKA surgery with either a cementless high-porosity trabecular-metal tibial component with a monobloc UHMWPE inlay (MONO-TM) or a cementless low-porosity screw-augmented titanium fiber-mesh tibial component with a modular UHMWPE inlay (MODULAR-FM). Radiostereometry was used to measure PE wear and tibial component migration.ResultsAt 60-month follow-up, mean PE wear of the medial compartment was 0.24 mm and 0.61 mm and mean PE wear of the lateral compartment was 0.31 mm and 0.82 mm for the MONO-TM and the MODULAR-FM groups, respectively (p < 0.01). The PE wear-rate was 0.05 mm (95% CI 0.03–0.08) in the MONO-TM group and 0.14 mm (95% CI 0.12–0.17) in the MODULAR-FM group (p < 0.01). Total translation at 60 months was mean 0.30 mm (95% CI 0.10–0.51) less (p < 0.01) for MONO-TM compared with MODULAR-FM tibial components. The majority of tibial components were stable (<0.2 mm MTPM) from 12 to 24-month and 24 to 60-month follow-up.ConclusionAt mid-term follow-up, monobloc PE inlay wear was approximately 40% of that of the modular PE inlay wear, which suggest that back-side wear of modular PE inlays is a significant contributor of PE wear in hybrid TKA.     

Evaluation of different coatings of the tibial tray in uncemented total knee arthroplasty. A randomized controlled trial with 5 years follow-up with RSA and DEXA

BackgroundRegenerex® is a porous titanium construct with a 3D interconnecting pore structure and biomechanical characteristics close to that of normal trabecular bone. This study aimed to compare the Regenerex (VR) to the non-interconnecting pore structure Porous Plasma Spray (VP) on tibial implants for total knee arthroplasty (TKA) at 5 years.MethodsWe enrolled and randomized 61 patients (mean age = 63(49–71) years, Female/Male = 35/26) who were planned for an uncemented Vanguard TKA (Biomet, Warsaw, Indiana, USA) to receive either a VR or a VP coated tibial component (31/29). We performed radiostereometric analysis (RSA) and Dual Energy X-ray Absorptiometry (DEXA) postoperatively, and at three, six, 12, 24 and 60 months with measurements of migration. In total 55 patients attended the 5-year follow-up.ResultsOne patient died and four were reoperated during the 60-months period; none due to aseptic loosening. All reoperations were in the VR-group. The mean (range) 60-months MTPM was 1.4 mm (0.5–3.7) for the VP-group and 1.8 mm (0.4–4.9) for the VR-group (p = 0.8). The 24 to 60-months mean (range) MTPM was −0.3 mm (−5 to 1.24) in the VP-group and 0.2 mm (−0.4 to 3.5) in the VR-group (p = 0.8).ConclusionWe did not find any statistically significant differences between the VP- and VR-group and both groups show recognizable migration. We will continue to follow the groups for years to come.     

Changes in bone mineral density of the distal femur after total knee arthroplasty: A 7-year DEXA follow-up comparing results between obese and nonobese patients

Background and purposePeriprosthetic femoral bone mineral density (BMD, g/cm²) decreases after total knee arthroplasty (TKA) as a result of the stress-shielding phenomenon. It is not known whether obesity has an effect on this phenomenon or not. The aim of this study was to assess long-term periprosthetic BMD changes after TKA and compare whether there is a difference between obese and nonobese patients.MethodsA total of 69 TKAs in 61 patients were performed, and BMD measurements of the distal femur were followed up to 7 years postoperatively. The patients were divided into two study groups according to their body mass index, and the groups were compared in relation to BMD and functional outcome.ResultsThe mean of periprosthetic bone loss during the 7-year follow-up varied from 10.3% to 30.6% depending on the region of interest (p < 0.0005). The highest bone-loss rates were detected during the first three postoperative months. A total of 26 patients were categorized as obese with a body mass index value of ≥ 30 kg/m². The obese patients' total periprosthetic BMD was higher at both baseline (8.6%) and 7 years after operation (p = 0.05) (15.2%).ConclusionPeriprosthetic bone loss around the femoral component continued for up to 7 years postoperatively. The loss of bone density was not associated with any negative clinical outcome in this study, but periprosthetic bone loss was of a smaller quantity in the obese which is probably due to higher weight induced stresses on bone.     

Cement penetration after patella venting

There is a high rate of patellofemoral complications following total knee arthroplasty. Optimization of the cement–bone interface by venting and suction of the tibial plateau has been shown to improve cement penetration. Our study was designed to investigate if venting the patella prior to cementing improved cement penetration.Ten paired cadaver patellae were allocated prior to resurfacing to be vented or non-vented. Bone mineral density (BMD) was measured by DEXA scanning. In vented specimens, a 1.6 mm Kirschner wire was used to breach the anterior cortex at the center. Specimens were resurfaced with standard Profix instrumentation and Versabond bone cement (Smith and Nephew PLC, UK). Cement penetration was assessed from Faxitron and sectioned images by a digital image software package (ImageJ V1.38, NIH, USA). Wilcoxon rank sum test was used to assess the difference in cement penetration between groups. The relationship between BMD and cement penetration was analyzed by Pearson correlation coefficient.There was a strong negative correlation between peak BMD and cement penetration when analyzed independent of experimental grouping (r² = ? 0.812, p = 0.004). Wilcoxon rank sum testing demonstrated no significant difference (rank sum statistic W = 27, p = 0.579) in cement penetration between vented (10.53% ± 4.66; mean ± std dev) and non-vented patellae (11.51% ± 6.23; mean ± std dev). Venting the patella using a Kirschner wire does not have a significant effect on the amount of cement penetration achieved in vitro using Profix instrumentation and Versabond cement.     

Bisphosphonate-laden acrylic bone cement: mechanical properties, elution performance, and in vivo activity

Cemented total hip replacements generally fail after 10-20 years, often due to implant loosening from bone resorption. Bisphosphonates such as zoledronic acid (ZA) and pamidronate (PAM) are potent inhibitors of bone resorption. The local delivery of bisphosphonates via acrylic bone cement could decrease osteolysis and prolong implant lifespan. Conflicting studies suggest that bisphosphonate loading may or may not reduce the mechanical properties of acrylic bone cement. We assayed acrylic bone cement laden with ZA or PAM at different concentrations and diluent volumes. Four-point bend testing and compressive testing indicated that high volumes of diluent (with or without bisphosphonate) significantly reduced bending modulus and compressive strength. Radiography and electron microscopy indicated that high diluent volumes generated abnormal acrylic bone cement structure. After 6 weeks of incubation in saline, only 0.9% w/w of the total bisphosphonate incorporated in acrylic bone cement eluted in vitro, indicating a slow elution rate. In vivo testing was performed using a rat model. Cement cylinders were inserted into incisions in rat distal femora and ZA delivered locally (via elution from acrylic bone cement) or systemically (via injection). At 4 weeks postoperatively, dual energy X-ray absorptiometry demonstrated no significant increase in local bone mineral density (BMD) adjacent to ZA-laden implants. In contrast, systemic ZA delivery (0.1 mg/kg) led to a large (48.6%) and significant increase in BMD. Thus, systemic delivery appears more effective than local delivery.     

Five-year results of a randomised controlled trial comparing cemented and cementless Oxford unicompartmental knee replacement using radiostereometric analysis

BackgroundCementless fixation is an alternative to cemented unicompartmental knee replacement (UKR). The aim of this study was to determine if cementless UKR fixation is as good as cemented by comparing the five-year migration measured radiostereometric analysis (RSA) in a randomised controlled trial.MethodsThirty-nine patients were randomised to receive either a cemented or a cementless Oxford UKR and were studied at intervals up to five years to assess migration with RSA and radiolucencies with radiographs.ResultsDuring the first year there was a small and significant amount of migration, predominantly in an anterior direction, of both the cemented (0.24 mm, SD 0.32, p = 0.01) and cementless (0.26 mm, SD 0.31, p = 0.00) femoral components. Thereafter there was no significant migration in any direction. At no stage was there any significant difference between the migrations of the cemented or cementless femoral components. During the first year, particularly the first three months, the cementless tibial components subsided 0.28 mm (SD 0.19, p = 0.00). This was significantly (p = 0.00) greater than the subsidence of the cemented tibial component (0.09, SD 0.19, p = 0.28). Between the second and fifth years there was no significant migration of either cemented or cementless tibial components.At five years radiolucent lines occurred significantly less with cementless (one partial) compared to cemented (six partial and one complete) tibial components.ConclusionsAs, between two and five years, there was no significant migration of cemented or cementless components, and no significant difference between them, we conclude that cementless fixation is as reliable as cemented. It may be better as there are fewer radiolucent lines.     

No difference in long-term outcomes between men and women undergoing medial fixed-bearing cemented unicompartmental knee arthroplasty: A retrospective cohort study with minimum 10-year follow up

BackgroundSome studies have suggested that women have poorer short-term outcomes after unicompartmental knee arthroplasty (UKA) due to a higher incidence of implant overhang. This study aimed to compare patient-reported outcome measures (PROMs) between men and women after UKA at a minimum follow-up of 10 years.MethodsPatients who underwent medial fixed-bearing UKA by two arthroplasty surgeons were identified from an institutional joint registry. Men and women were matched for age, body mass index, Charlson Comorbidity Index, American Society of Anesthesiologists class, range-of-motion and baseline PROMs using propensity scores. PROMs were compared at 2 and 10 years. Patients also completed a satisfaction questionnaire during these visits. Radiographic outliers were defined as > 2 mm of overhang.ResultsA total of 128 patients were included. There was no difference in complications, length of stay or readmissions. Women had poorer Knee Society functional scores, Short-Form 36 physical and mental component scores (SF-36 MCS) at 2 years. No difference in PROMs was found at 10 years, except for poorer SF-36 MCS in women (P = 0.041). At 10 years, 96% of women and 92% of men were satisfied (P = 0.243). Fifteen-year survivorship free from any revision was 96% in each group. There were more medial-tibial outliers in women (9%) compared with men (5%) (P = 0.018). However, no association between outliers and outcomes or survivorship was found on multivariate analyses.ConclusionThere was no difference in clinical outcomes between men and women undergoing UKA at a minimum follow-up of 10 years. While women had a higher incidence of medial tibial overhang, this was not associated with long-term outcomes or survivorship.     

Mid-term CT assessment of bone healing after nanohydroxyapatite augmentation in open-wedge high tibial osteotomy

BackgroundThe aim of the present study was to confirm the effectiveness of adding nanohydroxyapatite (NHA) to a heterologous bone graft in open-wedge high tibial osteotomy (OWHTO) by measuring the bone density via multislice computed tomography (CT) of the tibial osteotomy gap in a mid-term follow-up (five years).MethodsTwenty-six patients undergoing OWHTO were randomly assigned to two groups: a pure graft group (Group A), in which the osteotomy gap was filled with only heterologous bone graft, and an NHA group (Group B), in which the osteotomy gap was filled with heterologous bone graft and NHA. CT was performed within one week of the operation, after two months, after 12 months and after five years. CT volume acquired in Hounsfield units (HU) was measured on three planes.ResultsThe normal bone density was 110.2 ± 11.7 HU. The value of mean density at five years in Group A was 296.8 ± 81.8 HU, while in Group B, it was 202.2 ± 45.1 HU, showing a density more similar to normal bone and greater bone uniformity inside the osteotomy. The difference between the two groups was statistically significant (p < 0.05). Furthermore, both groups showed excellent mid-term clinical outcomes without significant differences.ConclusionsThis study revealed that absorbability and bone formation at the osteotomy site in the NHA group was significantly higher as compared with the pure graft group at five years postoperatively.     

Effect of gap balancing and measured resection techniques on implant migration and contact kinematics of a cementless total knee arthroplasty

BackgroundThe purpose of this study was to compare implant migration and tibiofemoral contact kinematics of a cementless primary total knee arthroplasty (TKA) implanted using either a gap balancing (GB) or measured resection (MR) surgical technique.MethodsThirty-nine patients underwent TKA via a GB (n = 19) or a MR (n = 20) surgical technique. Patients received an identical fixed-bearing, cruciate-retaining cementless implant. Patients underwent a baseline radiostereometric analysis (RSA) exam at two weeks post-operation, with follow-up visits at six weeks, three months, six months, and one year post-operation. Migration including maximum total point motion (MTPM) of the femoral and tibial components was calculated over time. At the one year visit patients also underwent a kinematic exam via RSA.ResultsMean MTPM of the tibial component at one year post-operation was not different (mean difference = 0.09 mm, p = 0.980) between the GB group (0.85 ± 0.37 mm) and the MR group (0.94 ± 0.41 mm). Femoral component MTPM at one year post-operation was also not different (mean difference = 0.27 mm, p = 0.463) between the GB group (0.62 ± 0.34 mm) and the MR group (0.89 ± 0.44 mm). Both groups displayed similar kinematic patterns.ConclusionsThere was no difference in implant migration and kinematics of a single-radius, cruciate retaining cementless TKA performed using a GB or MR surgical technique. The magnitude of migration suggests there is low risk of early loosening. The results provide support for using the cementless implant with either a GB or MR technique.     

Multiplanar correction of proximal tibial recurvatum deformity with tibial osteotomy and computer assisted fixator

BackgroundSeveral treatment modalities including open wedge osteotomies and Ilizarov reconstruction have been described for treatment of Proximal tibial recurvatum (PTR). However, the literature lacks information regarding the multiplanar correction of PTR using the computer assisted hexapod external fixator. The aim of the study is to present the results of PTR treatment with a computer assisted fixator systems.MethodsThere were three female and three male patients (10 lower extremities) with a mean age of 20.6 years (7.3 to 25.2y) in the study group. The angle of genu recurvatum (aGR), the tibial plateau tilt angle (aTP), the mechanical posterior proximal tibial angle (mPPTA) and sagittal mechanical axis deviation (MADs) was measured for the sagittal plane assessment.ResultsPreoperative sagittal assessment showed that the mean aGR was 28.9°±6.8°, mean aTP was 64.5°±10.2° and mean mPPTA was mPPTA was 114.1° ±10.3°. At the final follow-up there was a significant correction (p < 0.05 for aGR, aTP and mPPTA). Mean MADs was improved from 66.1 ± 14.2 mm to 16.6 ± 5.1 mm (p:0.005). Mean A:B ratio was 0.92 ± 0.13 preoperatively and 0.89 ± 0.14 postoperatively (p:0.37). Nine out of 10 knees had valgus deformity and mean preoperative tibiofemoral anatomic angle (TFA) was improved from 10.8°±3.7° valgus to 6.5°±1.7° valgus.ConclusionThe treatment of PTR deformity with a computer-assisted hexapod external fixator is safe and effective. It provides multiplanar correction of the deformity with a high precision and the patellar alignment remains stable during the correction.     

Histology of the bone-cement interface in retrieved Oxford unicompartmental knee replacements

IntroductionRadiolucent lines (RLL) are commonly seen at the cement–bone interface of knee replacements, yet are poorly understood. Although thin RLL are not associated with implant loosening or poor patient outcome there is still concern that they indicate sub-optimal fixation. The primary study aim is to characterise the histology at the cement–tibia interface in Oxford unicompartmental knee replacement (UKR). The second aim is to assess whether a correlation exists between the presence of a RLL and the type of tissue that predominates at the interface.MethodsThe radiology and histology of retrieved specimens of the interface from around firmly fixed tibial trays in ten patients undergoing revision between 1 and 19 years after Oxford UKR were studied.ResultsPre-revision radiographs showed the presence of both full and partial RLL. On contact radiographs of 5 mm thick sections of the interface the total percentage of radiolucency ranged from 0 to 90% between patients. There was no consistent pattern for the distribution of radiolucency. Histological assessment demonstrated that under every tibial component there were areas where there was direct contact and interdigitation between bone and cement. The amount of direct bone–cement contact was between 19% and 95% of the tibial tray surface area. The remaining tissue was mainly fibrocartilage but there was also fibrous tissue. The presence of radiolucency was strongly inversely correlated with the percentage of cement–bone contact.ConclusionThis study demonstrates that even with partial or complete RLL seen on radiographs there is still cement–bone contact, thus indicating that there is stable fixation.     

The natural history of radiolucencies following cemented unicompartmental knee arthroplasty at 7 years

IntroductionRadiolucent lines (RLLs) following unicompartmental knee arthroplasty (UKA) can be concerning as aseptic loosening remains a cause of failure in UKA. The aim of our study was to report on the history of RLLs surrounding the components in a cemented medial compartment fixed-bearing UKA as well as the long-term functional outcomes in this group of patients.Material and methodsIn this retrospective consecutive case-series, twenty-eight patients (37 knees) were treated with medial, fixed-bearing cemented unicompartmental knee arthroplasty. At average final follow-up of 7.1 years, 36 knees were available for review. Radiographs were taken at six weeks, one year, and final follow up. RLLs were measured using a novel modification to the Knee Society scoring (KSS) system.ResultsAt six-weeks, we identified RLLs in 26 tibias and two femurs out of 37 total knees. At one-year, four additional tibias and both femurs showed some progression of their radiolucencies but were < 2 mm total. At final follow-up, 31 of the 36 tibias (86.1%) and five of the 36 femurs (13.9%) had any RLLs. On the tibial side, RLLs were most common in medial/lateral and anterior/posterior aspects of the tibial tray with few found centrally. On the femoral side, the posterior femoral cut accounted for the most RLLs of any zone at all time points. KSS averaged 93.8 at final follow-up and none of the patients required revision surgery.ConclusionRLLs are common following cemented, fixed-bearing UKA. Many seem to progress slowly up to one year but not thereafter. There does not appear to be any association between the presence of these radiolucencies and long-term follow-up function in this group of patients.     

Implant fracture of the Regenerex® modular metal tibial component: A report of three cases

BackgroundImplant fractures are a very rare complication in primary total knee replacement (TKR) surgery and with modern implant designs and improved metals these events have nearly been eliminated. In this case series we report three cases of tibial metal baseplate fractures in uncemented Regenerex® TKR.MethodsCases originated from a prospective case series of 80 patients operated between 2013 and 2016. Five patients were pilot cases and 75 were participants in a prospective randomized double-blinded clinical trial that evaluated different adjuvant bone anti-resorptive medical therapies. All patients were treated with an uncemented press-fit Regenerex® Porous Titanium Construct tibial tray and matching cemented (Refobacin Bone Cement R) patella and femoral components (hybrid implant).ResultsWe report three cases of medial side metal baseplate fractures of a modular finned tibial stem. All three baseplate fractures were in male patients. Confirmed failure of the implant occurred after 10, 12 and 23 months, in situ, with a mean follow-up of 15 months (range 10-23).ConclusionsBased on the current case series we cannot make any causal inferences. Failures may represent a multifactorial process with a cascade of events with implant failure as the result. However, like in most other case reports of metal failures in the literature, the implant fractures in this report were located on the medial side of the tibial component in male patients.     

An original arthroscopic fixation of adult's tibial eminence fractures using the Tightrope® device: A report of 8 cases and review of literature

PurposeThe objective of this study is to asset the efficiency of the use of the Tightrope® device to treat isolated tibial spine fractures in adults.MethodsAll patients treated for isolated tibial spine fracture between November 2007 and February 2011 have been retrospectively included. The main judgment criteria was the post-operative knee laxity measured by Rolimeter® (Aircast) and the secondary criteria were the IKDC scores, the knee mobility, the Lachman test and the bone union. 8 patients have been included. The mean age was 34.2 years (± 12.5). The classification of Meyers and McKeever identified 5 types II, 2 types IIIa and 1 type IIIb. The mean follow-up period was 10 months.ResultsThe mean post-operative anterior knee laxity was 6 ± 2.14 mm for the operated side and 5.6 ± 1.85 mm for the opposite side. No significant difference was found (P = 0.73). According to the IKDC classification 3 patients were normal (A), 2 were nearly normal (B), 1 was abnormal (C) and 1 was very abnormal (D). The mean IKDC subjective score was 70.71 ± 17.56. All 8 fractures achieved union without elevation. 3 patients developed motion complications and 2 required an arthroscopic arthrolysis. No other significant complication was noted. The outcome was compared to the different series published during the last 10 years.ConclusionThe use of the Tightrope® device is a simple technique occurring a rigid fixation, allowing early rehabilitation with a high rate of arthrofibrosis.Level of evidenceLevel IV, case series.     

Association between bone mineral density and lumbar disc degeneration

ObjectivesHigher vertebral bone mineral density (BMD) has been found to be related with lumbar disc degeneration (LDD), while relationship between femoral neck BMD and LDD remains controversial. The aim of our research was to study the relationship between LDD and BMD of the lumbar spine and femoral neck.Study designThe study population consisted of 168 postmenopausal women (aged 63.3–75.0 years, mean 68.6 years) from the prospective OSTPRE and OSTPRE-FPS study cohorts. The severity of LDD was graded from T2-weighted MRI images using the five-grade Pfirrmann classification. Four vertebral levels (L1-L4) were studied (total 672 discs). The association between lumbar BMD and Z-score and the severity of LDD was studied separately for each vertebral level with AN(C)OVA analysis, using potential confounders as covariates.ResultsHigher lumbar BMD and Z-score were associated with more severe LDD at all studied levels (L1-L4): between L4-L5 disc and L4 BMD (p = 0.044) and L4 Z-score (p = 0.052), between L2-L3 disc and L3 BMD (p = 0.001) and at all other levels (p < 0.001). The mean degeneration grade of the studied discs was associated with the mean L1-L4 BMD and Z-score (p < 0.001). Statistical significance of any result did not alter after controlling for confounding factors. There was no significant association between femoral neck BMD and LDD.ConclusionsHigher lumbar BMD/Z-score were associated with more severe LDD. There was no significant association between femoral neck BMD and disc degeneration. Femoral neck BMD may be a more reliable measurement for diagnosing osteoporosis in postmenopausal women with degenerative changes in the lumbar spine.     

Long-term survivorship of total knee arthroplasty with a single-radius,high-flexion posterior stabilized prosthesis

BackgroundThe purpose of this study was to determine functional outcomes, implant survival rate, and complications of a single-radius, high-flexion posterior stabilized (PS) total knee prosthesis at a minimum follow up of 10 years for a consecutive series.MethodsThis retrospective observational study included 395 consecutive patients who underwent 585 single-radius, PS total knee arthroplasties (TKAs) between January 2009 and December 2009. Their functional outcomes, implant survival rates, radiological findings, and complications were evaluated.ResultsAt a mean follow up of 11.2 years (range, 10.6–11.8 years), 395 (80.8%) patients were available for review. At final follow up, preoperative Knee Society knee scores were improved from 37.3 to 80.1 (P < 0.05) and function scores were improved from 35.7 to 80.5 points (P < 0.05). Sixteen knees (2.7%) in 15 patients required revision surgery due to 11 septic loosening (1.9%) and five aseptic loosening events (0.8%). Cumulative survival for the prosthesis was 97.3% for any cause at 10 years. A total of 34 radiolucent lines (5.8%) were detected an average of 2.4 years following surgery and radiological assessment did not reveal any evidence of component migration at final follow up.ConclusionsSingle-radius, high-flexion PS TKA showed good long-term survival rates and clinical outcomes. Further study is required to determine whether limited radiolucency findings at the tibial component–tibial plateau could progress to or result in the loosening of components.