Abstract: Maquet III procedure, unloved due to its complications (2% to 59%), has been progressively abandoned. At long-term follow-up, what happens to patients with complications that exceeded the initial ones (Acta Orthop Scand 60:20, 1989)? We retrospectively studied patients who were submitted to Maquet III procedure, by functional and radiologic long-term outcomes, in order to determine if this surgery has or has not fulfilled its initially proposed objectives. From 1970 to 1991, 116 patients benefit from the Maquet III procedure. From this, we were able to review in 2011, 23 patients (25 knees) who went through a single Maquet III procedure. Of these patients, 52% were males. Age at surgery was 39.7 +/- 11.4, with a postoperative follow-up of 27.2 +/- 3.1 years.
METHODS:
A questionnaire has been prepared for collecting data, and it has been supplemented by clinical records. We evaluated the preoperative complaints, postoperative complications, and range of motion during the recovery time, as well as the postoperative pain-absence period. All patients underwent an objective assessment using the visual analog scale (VAS) at rest and activity, and the Kujala patellofemoral scoring system. A radiological assessment was also made in order to evaluate the arthrosis degree. The bicondylo-patellar angle described by Delgado-Martins (Arch Orthop Traumat Surg 96:303--304, 1980) was used to measure patellar tilt, and the Caton-Deschamps index to calculate the patellar height.
RESULTS:
Only one knee had benefited from a total knee arthroplasty (20 years after the Maquet III procedure). Preoperative complains were mainly anterior knee pain, crepitus, and patellar instability. Nowadays, 10 patients (40%) still are pain free. Others had an average period without pain of 19.1 +/- 6.1 years. VAS at rest was 1.7 +/- 0.7 and in activity 4.4 +/- 3.0. KPS was 61.9 +/- 22.3 points. X-ray shows that 40% had a Kellgren-Lawrence grade of 1 at the patellofemoral joint.
CONCLUSION:
Maquet proposed this technique for knee-pain relief, maintenance of the knee range of motion, and for slowly progressive osteoarthritic development. Viewed in a dispassionately way, we could notice that the initial objectives of this procedure were completely achieved. A part of 80% of the initial population was lost during follow-up, which may compromise the conclusions, perhaps, it is time to reflect again on this solution, so unloved by so many.
Abstract: Bone loss and subsequent defects are often encountered in revision total knee arthroplasty. In particular, when the cortical rim of proximal tibia is breached, the surgical decision on the reconstructive options to be taken is challenging due to the variety of defects and the lack of data from clinical or experimental studies that can support it. The purpose of this study is to assess how different reconstructive techniques, when applied to an identical defect and bone condition, can be associated to dissimilar longevity of the revision procedure, and the role of a stem in this longevity.
METHODS:
Proximal cortex strains and implant stability were measured in ten reconstructive techniques replicated with synthetic tibiae. The cancellous bone strains under each construct were assessed with finite element models which were validated against experimental strains.
FINDINGS:
The measured strains and stability showed that the proximal cortex is not immune to the different reconstructive techniques when applied to an identical defect. The largest cancellous strain differences between modular and non-modular techniques indicate a distinct risk between reconstructive techniques, associated to the supporting capacity of cancellous bone at long term.
INTERPRETATION:
The main finding of the present study is the observation that modular augments increases, on a long term basis, the potential risk of bone resorption relative to the non-modular techniques. In addition, the use of a press-fit stem in the scope of non-modular techniques can lead to improved stability and load transfer, which can contribute positively to the life expectancy of these techniques
Abstract: After anterior cruciate ligamentoplasty, anterior knee pain, sensibility and muscular strength deficits
are the most important variables affecting the final outcome of the well positioned neo-ligament,
being these outcomes intrinsically related to the type and location of the graft utilized.
Abstract: Total knee arthroplasty complications related to the prosthetic
material are very rare, except for polyethylene wear.
We report the case of a 58-year-old woman who came to the
emergency service of our hospital with a periprosthetic tibial
fracture (Mayo Clinic type I). Careful examination showed
that this fracture was concomitantly associated with a tibial
stem fatigue fracture. The prosthesis and the stem were sent
to an independent biomechanics laboratory for evaluation. A
finite-element CAD system was used to make a reconstruction,
so as to ascertain whether there had been any manufacturing
defect and what the causes of the event might have been. After
evaluation of several hypotheses, it was concluded that the
fracture in the prosthetic material had been caused by overloading
at the plate/stem transition zone secondary to previous
bone failure (fracture). From the evaluation of this case, the
need to make appropriate assessment of bone mineralization
can again be emphasized. In cases of doubt, a longer stem
should be used.
Abstract: Numerous models of elbow prostheses are being used and can be divided into two categories: one being a semi-constrained, linked type; and the other being non-constrained, unlinked type. Recent reports of National Elbow Arthroplasty Registers reveal no significant differences in the survival rates between linked and unlinked prosthesis brands, and the main cause appointed for revision for both types is loosening. Some previous biomechanical studies confirm the presence of abnormal bone stresses for the linked type, which can be associated with the risk of loosening. However for the unlinked type, biomechanical studies are not available that corroborate a loosening risk. It seems, that issue has not yet been fully answered and requires further analysis.
METHODS:
Cortex strains adjacent to the elbow joint were measured with strain gauges in synthetic humeri and ulnae, before and after replacement. To assess cancellous bone strains and cement stresses around the implant finite element models validated relative to measured strains were used.
FINDINGS:
Bone strains adjacent to the implant tip increased several times in the humerus and ulna. At the epiphyseal regions a generalised cancellous bone strain reduction was observed for both humerus and ulna relatively to the intact bones.
INTERPRETATION:
The unlinked elbow prostheses can be associated with the risk of bone fatigue failure by overload, particularly in the ulna, and bone resorption by stress-shielding at the epiphyseal regions. The identical structural behaviour relative to linked prostheses associated with the same loosening risks corroborates the results of recent arthroplasty published register reports.
Abstract: Background: Recognized failure mechanisms after revision total knee arthroplasty include failure of fixation,
instability and loosening. Thus, extended stems have been used to improve fixation and stability. In
clinical cases where the stem is only applied in the femur, a question concerning the structural aspect of
tibia may arise: Does a stemmed femur changes the structural behaviour of proximal tibia? It seems, that
question has not yet been fully answered and the use of stems in the opposite bone structure requires
further analysis.
Methods: Proximal cortex strains were measured with tri-axial strain gauges in synthetic tibias for three
different types of implanted femurs, with two constrained implants. To assess the strains at the cancellous
bone under the tibial tray, it was considered a closest physiological load condition with the use of
finite element models.
Findings: No significant differences of the mean of the tibial cortex strains for the stemmed femur relatively
to the stemless femur were observed. The R2 and slopes values of the linear regressions between
experimental and finite element strains were close to one indicating good correlations. The strain behaviour
of cancellous bone under the tibial tray is not completely immune to the use of femoral stem extensions.
However, the level of this alteration is relatively small when compared with the strain magnitudes.
Interpretation: The main insight given by the present study could probably lie in the fact that the use of
femoral stems does not contribute to an increase of the risk of failure of the tibia.
Abstract: Background: Recognized failure mechanisms after revision total knee arthroplasty include failure of fixation,
instability and loosening. Thus, extended stems have been used to improve fixation and stability. In
clinical cases where the stem is only applied in the femur, a question concerning the structural aspect of
tibia may arise: Does a stemmed femur changes the structural behaviour of proximal tibia? It seems, that
question has not yet been fully answered and the use of stems in the opposite bone structure requires
further analysis.
Methods: Proximal cortex strains were measured with tri-axial strain gauges in synthetic tibias for three
different types of implanted femurs, with two constrained implants. To assess the strains at the cancellous
bone under the tibial tray, it was considered a closest physiological load condition with the use of
finite element models.
Findings: No significant differences of the mean of the tibial cortex strains for the stemmed femur relatively
to the stemless femur were observed. The R2 and slopes values of the linear regressions between
experimental and finite element strains were close to one indicating good correlations. The strain behaviour
of cancellous bone under the tibial tray is not completely immune to the use of femoral stem extensions.
However, the level of this alteration is relatively small when compared with the strain magnitudes.
Interpretation: The main insight given by the present study could probably lie in the fact that the use of
femoral stems does not contribute to an increase of the risk of failure of the tibia.
Abstract: Theoretical concerns about the use of cemented or press-fit stems in revision total knee arthroplasty (TKA) include stress
shielding with adverse effects on prosthesis fixation. Revision TKA components are commonly stemmed to protect the limited
autogenous bone stock remaining. Revision procedures with the use of stems can place abnormal stresses through even normal
bone by their constrained design, type of materials and fixation method and may contribute for bone loss. Experimental quantification
of strain shielding in the proximal synthetic tibia following TKA is the main purpose of the present study. In this study, cortical
bone strains were measured experimentally with tri-axial strain gauges in synthetic tibias before and after in vitro knee surgery.
Three tibias were implanted with cemented and press-fit stem augments and solely with a tibial tray (short monobloc stem) of
the P.F.C. Sigma Modular Knee System. The difference between principal strains of the implanted and the intact tibia was calculated
for each strain gauge position. The results demonstrated a pronounced strain-shielding effect in the proximal level, close to
tibial tray with the cemented stem augment. The press-fit stem presented a minor effect of strain shielding but was more extensively
throughout the stem. An increase of strains closely to the distal tip of the cemented and the press-fit stem augment was observed.
This suggests for a physiological condition, a potential effect of bone resorption at the proximal region for the cemented stem
augment. The localized increase of strains in stems tip can be related with the clinical finding of the pain, at the end of stem after
revision TKA.
Abstract: Total Knee Arthroplasty (TKA) changes mechanical loading of the knee joint. Bone loss in the tibia is commonly encountered at the time of the
revision TKA. Restoration of lost bone support and joint stability are the primary challenges in revision TKA. Normally, these defects are treated
with non-living structures like metallic augments or bone grafts (autografts or allografts). Alone, neither of these structures can provide the initial
support and stability for revision implants. In the latter, the use of intramedullary stems can provide the necessary load sharing and protect the
remaining host bone and graft from excessive stress, increasing component stability. The purpose of this study was to evaluate comparatively load
sharing (cortical rim, cancellous bone and stem) and stability at the cement–bone interface under the tibial tray induced by the use of cemented
and press-fit tibial component stem extensions. Furthermore the study of the desirable option in cases where the bone defect is cavitary (cancellous
bone defect contained by an intact cortical rim) or uncontained bone defect (bone loss involving the supporting cortical rim) was carried out.
Because in vitro evaluation of these biomechanical parameters is difficult we used finite element (FE) models to overcome this. The
biomechanical results suggest an identical behaviour in case of cavitary defects for both
Abstract: Finite Element (FE) models for the simulation of intact
and implanted bone find their main purpose in accurately
reproducing the associated mechanical behavior. FE models
can be used for preclinical testing of joint replacement
implants, where some biomechanical aspects are difficult,
if not possible, to simulate and investigate in vitro. To
predict mechanical failure or damage, the models should
accurately predict stresses and strains. Commercially
available synthetic femur models have been extensively
used to validate finite element models, but despite the
vast literature available on the characteristics of
synthetic tibia, numerical and experimental validation of
the intact and implant assemblies of tibia are very
limited or lacking. In the current study, four FE models
of synthetic tibia, intact and reconstructed, were
compared against experimental bone strain data, and an
overall agreement within 10% between experimental and FE
strains was obtained. Finite element and experimental
(strain gauge) models of intact and implanted synthetic
tibia were validated based on the comparison of cortex
bone strains. The study also includes the analysis carried
out on standard tibial components with cemented and
noncemented stems of the P.F.C Sigma Modular Knee System.
The overall agreement within 10% previously established
was achieved, indicating that FE models could be
successfully validated. The obtained results include a
statistical analysis where the root-mean-square-error
values were always <10%. FE models can successfully
reproduce bone strains under most relevant acting loads
upon the condylar surface of the tibia. Moreover, FE
models, once properly validated, can be used for
preclinical testing of tibial knee replacement, including
misalignment of the implants in the proximal tibia after
surgery, simulation of long-term failure according to the
damage accumulation failure scenario, and other related
biomechanical aspects.
