Symptomatic total knee arthroplasty

2.4.1 Reasons for revisions and unsatisfied patients

Despite many advances in primary TKA surgical technique, patient selection, and implant design, studies that report postoperative patient satisfaction indicate rates of only 82% to 89% (Anderson, et al. 1996, Chesworth, et al. 2008, Bourne, et al.

2010). Patient satisfaction is an important outcome measure since there often is a discrepancy between the surgeon-driven objective scales and the patient reported outcome measures (Mantyselka, et al. 2001, Janse, et al. 2004, Noble, et al. 2006). The reasons for revision knee arthroplasty vary according to different national registries (Lygre, et al. 2011, Siqueira, et al. 2015), in part because the registries often fail to represent standardized definitions for the modes of failure. For example, pain is not included as a reason of revision in the Swedish registry, and instability is not rec-ognized in the registry of New Zealand. The British registry does not include a

sep-The remodeling

The femoral stress shielding may be derived by the shape of the component. The components of a modern TKA are “cup-shaped” which may protect the distal met-aphyseal femoral bone from stresses below the anterior and posterior surfaces. This combined with the protection of the anterior flange of the prosthesis against the shear forces of the extensor apparatus transmitted by patella (7 times the body weight at 45 degrees of knee flexion) may be the explanation of the phenomenon (Van Lenthe, et al. 1997, Karbowski, et al. 1999, van Loon, et al. 2001). The shape of the tibial component of a commonly used non-constrained tibial prosthesis is more or less flat with a short stem. The stability of the component is thought to be de-pendent on the proximal metaphyseal bone of the tibia (Petersen, et al. 1995, Taylor, et al. 1998, Li and Nilsson. 2000a, Soininvaara, et al. 2004b). Malalignment of a tibial component causes abnormal load distribution. This may induce abnormal bone remodeling beneath the component, leading to insufficient supportive strength of the proximal tibial bone (Felix, et al. 1997, Thompson, et al. 2001). Furthermore, poor bone quality and low BMD may even contribute to migration of the compo-nent (Andersen, et al. 2017).

2.3 INHIBITORS OF BONE RESORPTION – BISPHOSPHO-NATES

Bisphosphonates are an effective and widely used medication in bone disorders when the inhibition of bone resorption is needed; osteoporosis is the most common indication (Cranney, et al. 2002, Wells, et al. 2008). Nonetheless, concerns have recently been raised about their safety in long-term use (Abrahamsen. 2010). Re-ports have appeared on harmful effects such as atypical femoral shaft fractures and osteonecrosis of the jaw, but their risks are still considered to be relatively low when balanced against the positive effects of the medication (Khosla, et al. 2012).

The efficacy of alendronate was clearly highlighted in a Cochrane database analysis of the secondary prevention of all osteoporotic fractures and in the primary preven-tion of vertebral fractures (Wells, et al. 2008).

The benefit of alendronate treatment after TKA has remained controversial, and only a few studies on this issue have been conducted. In one study, distal femoral bone BMD increased 10% at six months, and a significant BMD-preserving effect was maintained up to the three-year follow-up assessment (Wang, et al. 2003).

However, there have also been contrasting results published, with alendronate showing no effect on periprosthetic BMD after TKA (Abu-Rajab. 2009). There are additional studies supporting the short-term bone-preserving effect of alendronate treatment after total hip arthroplasty (THA) (Venesmaa, et al. 2001, Yamaguchi, et al. 2004, Yamasaki, et al. 2007, Trevisan, et al. 2010, Iwamoto, et al. 2011). However, long-term studies are scarce (Tapaninen, et al. 2010). The preventive impact on pos-sible prosthesis component migration is even more controversial. In one study there was a preventive effect (Hilding, et al. 2000), but it was not confirmed in another study (Hansson, et al. 2009).

2.4 SYMPTOMATIC TOTAL KNEE ARTHROPLASTY

2.4.1 Reasons for revisions and unsatisfied patients

Despite many advances in primary TKA surgical technique, patient selection, and implant design, studies that report postoperative patient satisfaction indicate rates of only 82% to 89% (Anderson, et al. 1996, Chesworth, et al. 2008, Bourne, et al.

2010). Patient satisfaction is an important outcome measure since there often is a discrepancy between the surgeon-driven objective scales and the patient reported outcome measures (Mantyselka, et al. 2001, Janse, et al. 2004, Noble, et al. 2006). The reasons for revision knee arthroplasty vary according to different national registries (Lygre, et al. 2011, Siqueira, et al. 2015), in part because the registries often fail to represent standardized definitions for the modes of failure. For example, pain is not included as a reason of revision in the Swedish registry, and instability is not rec-ognized in the registry of New Zealand. The British registry does not include a

sep-arate category for patellofemoral complications (Siqueira, et al. 2015). Nevertheless, component loosening, infection, pain, patellofemoral problems, instability and pol-yethylene wear are often reported to be the most common reasons for revisions in register data (Finnish Arthroplasty Register, Sadoghi, et al. 2013, Siqueira, et al.

2015). Reasons for early failure (within the first 2 years after surgery) can be as-sumed to be primarily caused by the surgical procedure itself while late failures more likely are implant related (Graichen. 2014). The most prominent reason for early failure is infection (Mayle, et al. 2012). Other reasons include malpositioning of the components, instability and patellofemoral problems. For the late failure, aseptic implant loosening becomes more often the reason (Graichen. 2014).

Although TKA carries a high survivorship, it is less clear whether it confers ade-quate functional benefits to patients and whether they are considered successful by the patients themselves. The patient-reported reasons for dissatisfaction differ from the ones for TKA revision. Patients who experienced more pain and functional im-pairment after TKA are less likely to be satisfied with the procedure, with pain be-ing a stronger determinant than function (Robertsson, et al. 2000, Baker, et al. 2007).

Patient expectation also plays a critical role in eventual outcome and satisfaction.

Patients with higher expectations are more likely to be dissatisfied (Noble, et al.

2006, Parvizi, et al. 2014). Patient age is a more controversial determinant of satis-faction. Some studies indicate that younger age is a predominant factor for dissatis-faction (Noble, et al. 2006, Parvizi, et al. 2014), but results demonstrating that pa-tients aged 50 years or younger having similar satisfactory rate to those of non–age-restricted populations have also been reported (Goh, et al. 2017). Elderly patients were not more dissatisfied than others in a Swedish register data (Robertsson, et al.

2000), but a correlation for poorer satisfaction with advancing age has also been reported (Bourne, et al. 2010).

2.4.2 Clinical evaluation

The clinical evaluation of a symptomatic TKA requires a thorough history and physical examination. The primary symptom (pain, instability, swelling, stiffness) of the patient should be identified. The examination of the knee should evaluate an active and passive range of motion, varus and valgus stability in flexion and exten-sion, stability in the sagittal plane at 60 and 90 degrees of flexion to assess for mid-flexion and mid-flexion stability, manual strength testing, palpation for swelling or focal tenderness, and evaluation of patellofemoral stability and patellofemoral pain. The appropriate radiographs (full weight bearing knee projections and a mechanical axis evaluation) should also be assessed. Laboratory analysis specifically evaluating the inflammatory markers (erythrocyte sedimentation rate and C-reactive protein), along with a synovial fluid aspirate evaluating the white blood cell count with dif-ferential and culture should be examined if any sing or suspicion of infection is

present. Advanced imaging modalities are sometimes helpful when the diagnosis remains unclear. There is a consensus in the literature that revision surgery should be performed only if the causative mechanism for failure is well understood (Fehring, et al. 2001, Dennis. 2007, Fehring, et al. 2008, Mandalia, et al. 2008, Toms, et al. 2009, Cercek, et al. 2015, McDowell, et al. 2016). During the last decade, specif-ic diagnostspecif-ic algorithms to guide the evaluation of symptomatspecif-ic TKA have been developed (Hofmann, et al. 2011, Djahani, et al. 2013).

2.4.3 Computed tomography (CT)

TKA component malalignment problems in the axial plane (rotational alignment) are associated with limited and painful range of motion, patellofemoral joint mis-match, anterior knee pain, and even implant loosening or TKA failure leading to revision surgery (Berger, et al. 1998, Matsuda, et al. 2001, Bell, et al. 2014). The as-sessment of component rotation requires a CT scan, scatter reduction software and correct understanding of the reference axes (Victor. 2009). 2-D CT scan has been reported to have moderate to good intra- and inter-observer reliability (Konigsberg, et al. 2014). The recent literature shows a strong preference for enhancing the relia-bility with 3-D CT scans (De Valk, et al. 2016). Revision surgery for component mal-rotation detected by CT protocol has been reported to be as beneficial for the pa-tient as a revision for the indication of aseptic loosening (Sternheim, et al. 2012).

Cone beam computed tomography (CBCT) uses a single x-ray source and a flat panel detector. Multiple planar images are produced as the x-ray source and detec-tor rotates around the studied object. A single rotational (210°) sequence captures enough data for volumetric image construction, which reduces the radiation expo-sure significantly. The images are then mathematically reconstructed into a volu-metric dataset with isotropic voxels. The technique is widely used in periodontolo-gy, and a method of choice in dental implant imaging (Tyndall, et al. 2012, Aljehani.

2014). The development of dedicated CBCT imaging systems for musculoskeletal extremities opens whole new indications for the use of this technology (Zbijewski, et al. 2011). The radiation dose is substantially lower than in conventional multi-slice computed tomography (MSCT) devices (Koivisto, et al. 2013) and can even be further lowered with a radiation shield developed for the equipment (Matikka and Viren. 2014). A study on the capability of CBCT in imaging the knee joint has had promising results (Kokkonen, et al. 2014). However, at the time of this thesis, there is only one previously published study on the -evaluation of component rotation using CBCT (Nardi, et al. 2017) and none concerning TKA component loosening.

arate category for patellofemoral complications (Siqueira, et al. 2015). Nevertheless, component loosening, infection, pain, patellofemoral problems, instability and pol-yethylene wear are often reported to be the most common reasons for revisions in register data (Finnish Arthroplasty Register, Sadoghi, et al. 2013, Siqueira, et al.

2015). Reasons for early failure (within the first 2 years after surgery) can be as-sumed to be primarily caused by the surgical procedure itself while late failures more likely are implant related (Graichen. 2014). The most prominent reason for early failure is infection (Mayle, et al. 2012). Other reasons include malpositioning of the components, instability and patellofemoral problems. For the late failure, aseptic implant loosening becomes more often the reason (Graichen. 2014).

Although TKA carries a high survivorship, it is less clear whether it confers ade-quate functional benefits to patients and whether they are considered successful by the patients themselves. The patient-reported reasons for dissatisfaction differ from the ones for TKA revision. Patients who experienced more pain and functional im-pairment after TKA are less likely to be satisfied with the procedure, with pain be-ing a stronger determinant than function (Robertsson, et al. 2000, Baker, et al. 2007).

Patient expectation also plays a critical role in eventual outcome and satisfaction.

Patients with higher expectations are more likely to be dissatisfied (Noble, et al.

2006, Parvizi, et al. 2014). Patient age is a more controversial determinant of satis-faction. Some studies indicate that younger age is a predominant factor for dissatis-faction (Noble, et al. 2006, Parvizi, et al. 2014), but results demonstrating that pa-tients aged 50 years or younger having similar satisfactory rate to those of non–age-restricted populations have also been reported (Goh, et al. 2017). Elderly patients were not more dissatisfied than others in a Swedish register data (Robertsson, et al.

2000), but a correlation for poorer satisfaction with advancing age has also been reported (Bourne, et al. 2010).

2.4.2 Clinical evaluation

The clinical evaluation of a symptomatic TKA requires a thorough history and physical examination. The primary symptom (pain, instability, swelling, stiffness) of the patient should be identified. The examination of the knee should evaluate an active and passive range of motion, varus and valgus stability in flexion and exten-sion, stability in the sagittal plane at 60 and 90 degrees of flexion to assess for mid-flexion and mid-flexion stability, manual strength testing, palpation for swelling or focal tenderness, and evaluation of patellofemoral stability and patellofemoral pain. The appropriate radiographs (full weight bearing knee projections and a mechanical axis evaluation) should also be assessed. Laboratory analysis specifically evaluating the inflammatory markers (erythrocyte sedimentation rate and C-reactive protein), along with a synovial fluid aspirate evaluating the white blood cell count with dif-ferential and culture should be examined if any sing or suspicion of infection is

present. Advanced imaging modalities are sometimes helpful when the diagnosis remains unclear. There is a consensus in the literature that revision surgery should be performed only if the causative mechanism for failure is well understood (Fehring, et al. 2001, Dennis. 2007, Fehring, et al. 2008, Mandalia, et al. 2008, Toms, et al. 2009, Cercek, et al. 2015, McDowell, et al. 2016). During the last decade, specif-ic diagnostspecif-ic algorithms to guide the evaluation of symptomatspecif-ic TKA have been developed (Hofmann, et al. 2011, Djahani, et al. 2013).

2.4.3 Computed tomography (CT)

TKA component malalignment problems in the axial plane (rotational alignment) are associated with limited and painful range of motion, patellofemoral joint mis-match, anterior knee pain, and even implant loosening or TKA failure leading to revision surgery (Berger, et al. 1998, Matsuda, et al. 2001, Bell, et al. 2014). The as-sessment of component rotation requires a CT scan, scatter reduction software and correct understanding of the reference axes (Victor. 2009). 2-D CT scan has been reported to have moderate to good intra- and inter-observer reliability (Konigsberg, et al. 2014). The recent literature shows a strong preference for enhancing the relia-bility with 3-D CT scans (De Valk, et al. 2016). Revision surgery for component mal-rotation detected by CT protocol has been reported to be as beneficial for the pa-tient as a revision for the indication of aseptic loosening (Sternheim, et al. 2012).

Cone beam computed tomography (CBCT) uses a single x-ray source and a flat panel detector. Multiple planar images are produced as the x-ray source and detec-tor rotates around the studied object. A single rotational (210°) sequence captures enough data for volumetric image construction, which reduces the radiation expo-sure significantly. The images are then mathematically reconstructed into a volu-metric dataset with isotropic voxels. The technique is widely used in periodontolo-gy, and a method of choice in dental implant imaging (Tyndall, et al. 2012, Aljehani.

2014). The development of dedicated CBCT imaging systems for musculoskeletal extremities opens whole new indications for the use of this technology (Zbijewski, et al. 2011). The radiation dose is substantially lower than in conventional multi-slice computed tomography (MSCT) devices (Koivisto, et al. 2013) and can even be further lowered with a radiation shield developed for the equipment (Matikka and Viren. 2014). A study on the capability of CBCT in imaging the knee joint has had promising results (Kokkonen, et al. 2014). However, at the time of this thesis, there is only one previously published study on the -evaluation of component rotation using CBCT (Nardi, et al. 2017) and none concerning TKA component loosening.