The total population examined in the present thesis consists of 234 patients from four subgroups who had undergone TKA or UKA in Kuopio University Hospital during the time period from 1991–2007.
The patients’ characteristics including age, gender, medication, smoking, preoperative body mass index (BMI) and postoperative hospital stay were recorded from the medical case records. All the operations were carried out in the Department of Orthopaedics and Traumatology in Kuopio University Hospital and with the standard surgical technique and all prostheses were implanted in bone cement (Palacos cum gentamycin, Schering-Plough, US). All patients received 3g cefuroxime at induction, 40 mg/kg tranexamic acid intravenously immediately after the operation and 40 mg sodium enoxaparin ten days’
postoperatively.
The duration of the operation, post-operative bleeding and transfusions were recorded.
Chronic diseases of the patients (ASO, hypertension, diabetes, cancer, or cardiac illness), medication, smoking, preoperative range of motion and the need for ambulatory support for walking (e.g. crutches, walker) were recorded. Long, weight-bearing coronal and sagittal radiographs of the operated limb were examined. The alignment of the knee was evaluated, and the degree of the deviation of the mechanical axis was defined as the angle between a line from the femoral head to the centre of the knee joint and a line from the centre of the knee to the centre of the ankle. A deviation of less than ± 3 degrees from neutral was considered to be an acceptable outcome. The operations were performed using a tourniquet and spinal anesthesia.
The approval of the local ethics committee was sought and obtained separately for each single study project.
4.1.1 BMI and short-term outcome after TKA (Study I)
Between October 2006 and March 2007, 100 primary unilateral TKA were performed in Department of Orthopedics and Traumatology, Kuopio University Hospital. The NexGen, posterior stabilized (PS) total knee prosthesis system (Zimmer, Warsaw, IN, USA) was implanted in 53 patients. The Triathlon cruciate retaining (CR) (Stryker Howmedica Osteonics, Mahway, NJ, USA) system was used in 46 patients and one operation was performed with Thriathlon posterior stabilized components. Each patient had a drain installed postoperatively. A total of 14 patellar surfacing (6 in Group 1 vs. 8 in Group 2) and 13 lateral releases (9 in Group 1 vs. 4 in Group 2) were performed. The consecutive patients were examined by an orthopedist approximately two weeks before the operation when their suitability for the procedure was evaluated.
The patients were invited to the Kuopio University Hospital for a control evaluation on an average at 3 months postoperatively. The patients were examined with a routine clinical procedure. The length of the wound was measured with a measuring tape with the knee as straight as possible, and ROM was measured with goniometry. Any postoperative complications were recorded. The level of pain was documented by asking the patients to rate it with a VAS. The patients' satisfaction with the operation was asked with a question, whether they would be willing to undergo again the same operation in the same situation: possible answers were ‚yes‛ or ‚no‛. The postoperative walking ability and balance were measured with a timed Get- Up- and- Go test. The mechanical axis of the lower limb was measured from the long, weight-bearing coronal and sagittal radiographs of the operated limb. A deviation of less than ± 3 degrees from neutral was considered to be a good outcome (Sampath et al. 2009).
The patients were divided into two groups (obese and non-obese) according to body mass index. Group 1 (non-obese, n = 48) consisted of patients whose body mass index was
< 30 kg/m 2 and the patients with BMI ≥ 30 kg/m2 made up Group 2 (obese, n = 52). The mean body mass index in Group 1 was 26.1 kg/m2 (22.2 − 29.4); in Group 2 it was 33.0 kg/m2 (30.0 − 40.5). The patients’ demographic data are shown in table 2.
The mean of the Kellgren-Lawrence classification was 3.1 (3.0−3.3) for the entire study population. There was no difference between the study groups in the radiological degree of severity of the osteoarthritis or the mechanical axis of the lower limb before operation:
KL: 3.2/3.1, p = 0.30; Mech. axis 8.0°/6.9°, p = 0.83. The preoperative deviation from the straight mechanical axis was at least 3 degrees in 39 patients in Group 1 and in 45 patients in Group 2, p = 0.46.
Table 2. Demographic data of the patients in study I expressed as number and mean (range).
Group 1(n = 48)
a ASO, hypertension, diabetes, cancer and cardiac illness.
b Glucocorticoids, salazopyrin and cytostatics.
4.1.2 BMI and long-term outcome after TKA (Study II)
Between May 1997 and May 2000, a total of 95 knee arthroplasties were performed in the Department of Orthopaedics and Traumatology, Kuopio University Hospital, in 85 randomly selected patients who met the inclusion criteria: no previous knee or hip operations, no medication or diseases known to influence bone mineral metabolism. Two other TKA studies were conducted at the same time and those patients were not included into this study. After obtaining the approval of the ethics committee of the University of the Kuopio, the current study continued until March 2009 by inviting all living patients to a follow-up examination. Eighteen patients had died (1997-2009) during the follow-up and in addition, 27 patients were not able to participate because of miscellaneous reasons (unfit n = 8, change of residence n = 2, cancelled without stating reason n = 17). The final follow-up cohort consisted of 48 TKA patients and 52 knees. The minimum duration of the follow-up period was nine years (mean 10.8 years, range 9-12 years). The mean age of the patients at the time of follow-up examination (April 2009) was 76.3 years (54−90, SD 6.7).
Four knee implant designs from four manufacturers were used: AMK (n = 8) (DePuy, Warsaw, IN, USA), AGC (n = 2) (Biomet Merck, Limited, Bridgend, South Wales, UK), Duracon (n = 25) (Stryker, Howmedica, NJ, US) and Nexgen (n = 17) (Zimmer, Warsaw, IN, US). A posterior cruciate retaining technique was performed with 46 knees and both anterior and posterior cruciate ligaments were removed in six cases.
The clinical and radiological evaluations were performed preoperatively, and at the follow-up visits (1-year postoperatively and April 2009). The clinical evaluations included the Knee Society clinical rating system (KSS) which contains two components of assessments (Knee score (KS) for assessing the condition of the knee and the prostheses and Function score (FS) for measuring the patient’s functional abilities) with a maximum of 100 score for each parameter (Insall et al. 1989). The knee score evaluates pain, range of motion (ROM) and knee stability, the function score evaluates walking distance, ability to climb stairs and the need for ambulatory supports.
The clinical evaluation also included Western Ontario and McMaster Universities Osteoarthritis index (WOMAC), and the Timed- Up-and Go-test. An extensive medical examination and interview were also performed.
There were 43 knees with preoperative varus deformity (mean 10.3°, SD 5.4) and 9 knees with preoperative valgus deformity (mean 7.7°, SD 4.5). The mean age of the patients at the time of the follow-up examination (April 2009) was 76.3 years (54−90, SD 6.7).
The patients were divided into two study groups according to the value of their body mass index (BMI). BMI was calculated by dividing the subject’s weight in kilograms by their height in meters squared (kg/m2). BMI was categorized as non-obese (Group 1) and obese (Group 2). Group 1 consisted of patients whose body mass index was < 30 kg/m 2 (non-obese, n = 26 preop/1-year; n = 23 spring 2009) and the patients with BMI ≥ 30 kg/m2 were designated into Group 2 (obese, n = 22 preop/1-year; n = 25 spring 2009). A total of five patients in the primary group 1 had gained and two patients in the primary group 2 had reduced their weight over the cut-off line during the mean of 10.8 years’ follow-up.
4.1.3 Primary TKA and UKA revision patients (Study III)
During 1991-2000, a total of 2949 knee, 344 unicompartmental knee and 484 revision knee arthroplasties were performed in the Department of Orthopaedics and Traumatology, Kuopio University Hospital. During this time period, 44 revisions needed to be performed on failed medial unicompartmental knee arthroplasties. Primary UKA operations were performed with Duracon, Kirschner, Link Endomodel, Miller-Galante and PCA semiendoprosthesis. All of these UKA revision patients included in this study had primarily medial unicompartmental knee osteoarthritis. The decision to perform the primary UKA was made by the surgeon during the operation. After approval by the ethics committee of Kuopio University, the project started in May 2008 by sending the patients a letter of invitation to attend a control examination in Kuopio University Hospital. Sixteen UKA revised patients had died during this time period (1991−2008) and six UKA revised patients, because of different reasons (dysphoria n = 2, cancelled without reporting the reason n =2, excellent knee n = 2), were not able to participate in this study. Furthermore, one patient did not fit the inclusion criteria because her UKA had been converted to a new UKA. Thus a total of 21 of the original 44 UKA revision patients were available with a minimum of 8 years follow-up (mean, 10.5 years; range 8−17 years) and are included in this report.
In many studies, the outcome after UKA revision operations has been reported to be comparable to that achieved in primary TKA operations (Levine et al. 1996, Chakrabarty et al. 1998, Foong et al. 2014). In this present study, the UKA revision patients (Group 1) were compared to a randomly selected group of TKA patients (n = 56) (Group 2) whose age, sex and the operation time point were comparable to those in Group 1. The number of control patients was based on the living UKA revision cases multiplied by 2. Patients for the control group were randomly selected from the population of TKA patients having the same age, gender and operation time distributions as UKA revised patients. Sixteen patients had died in this group and 12 patients were not able to participate in this study for miscellaneous reasons (dysphoria n = 4, cancelled without reporting a reason n = 5, bed patient n = 1, not able to communicate n = 1, moved n = 1). Thus TKA group (Group 2) consisted of 28 patients who had undergone primary TKA operation at the same time as the UKA patients had undergone the revision operation. Hence the final study population consisted of 49 patients (Group 1, n = 21, Group 2, n = 28).
The time from primary UKA to UKA revision as well as the mode of failure and requirement of augments, stems and bone grafts was recorded. Four knee implant designs from three manufacturers had been used for revision operation: AMK (1) (Depuy, Warsaw, IN, USA), Duracon (6) (Stryker Howmedica, NJ, USA), Miller-Galante (3) (Zimmer, Warsaw, IN, USA) and NexGen (11) (Zimmer, Warsaw, IN, USA). The first follow-up visit was scheduled at approximately 3 months after the operation for patients in both groups. The postoperative 3-month range of motion (ROM) and postoperative complications were also recorded for the first time at that visit.
The patients were invited to come to the Kuopio University Hospital for follow-up control at June 2008 and a detailed clinical examination and interview were performed.
The knee status included: ROM, stability, pain, cicatrix length and self-reported walking
distance. Walking ability and balance were measured with timed Up- and Go-test. The characteristics, with the exception of their smoking habits. Demographic values and descriptive statistics are shown in Table 3. The postoperative hospital stay for the patients who underwent UKA revision averaged 8.3 days (SD 1.05, range 8−11) and for the patients who underwent primary TKA 7.9 days (SD 1.83, range 6−12).
Table 3. Demographic data of the 49 patients in study III (SD).
Group 1 (n = 21)
In study IV, the subjects partially consisted of the same population as in study II. The fourth study focused on assessing the long-term changes in the bone mineral density of the distal femur between obese and non-obese patients. All the operations and DXA-based follow-up measurements were carried out between 1997 and 2007. Unfortunately, not all patients were able to participate in each of the DXA measurements which led to a loss of the study population during follow-up. Three patients had died and furthermore some had a poor health status or expressed a subjective desire to quit. Therefore, 61 patients (with 69 knees) were able to participate in the final DXA investigation at a mean of seven years after the operation (Duracon n = 34, Nexgen n = 21, AMK n = 11, AGC n = 3).
BMD (g/cm2) of the distal femur was measured at baseline, 3- and 6- months postoperatively and 1-, 2-, 4- and 7-years follow-up by using a fan-beam dual X-ray absorptiometry (Expert XL, Lunar Co., Madison, WI). The regions of interest (ROIs 1-5) were both metaphyseal and diaphyseal (Fig. 2).
The clinical evaluation of the patients was performed preoperatively and at each postoperative follow-up visit. The clinical evaluation included the Knee Society clinical rating system evaluation (KSS) which contains two different components: Knee Score (KS) and Function Score (FS) with a maximum value of 100 points for each component. A detailed medical examination and interview were also conducted at each visit.
The patients were divided into two study groups according to BMI. Group 1, non-obese (n = 35 patients/ 39 knees), consisted of patients whose body mass index was < 30 kg/m2.
Group 2, obese (n = 26 patients/ 30 knees), consisted of patients whose BMI was ≥ 30 kg/m2. The basic demographic data of the patients in study IV is expressed in table 4.
Table 4. Demographic data of 61 OA patients in study IV.
Description Number/mean
Bone mineral density (g/cm2) was analyzed using the software algorithm provided by the manufacturer. This enables the quantization of bone mineral density in the presence of metal in the scanning field. In order to minimize operator-related inaccuracies associated with manual drawing, no attempt was made to exclude the cement mantel from the analysis. During the lateral scan, the patient lay on his/her side with the knee flexed at an angle of 15 degrees and two repeated scans were performed. The prostheses flanges were used for determining the location of regions of interest (ROI).
After locating the ROIs manually for the first scan, the ‛compare facility ‛ of the software was used for copying the ROIs for the second and repeated scans during follow-up. Apart from using Lunar manuals, also a personal communication from the Lunar Company was provided to help with the edge-detection algorithms and recommendations on the exploitation of plastic backgrounds for better and more reliable definition of bone, soft tissue and air outlines (Soininvaara 2005).
Figure 2. Periprosthetic regions of interest (ROIs) of the distal femur: ROI1 Anterior metaphyseal, ROI2 Central, ROI3 Posterior, ROI4 Diaphyseal and ROI5 Total metaphyseal, marked with arrow = ROIs 1+2+3.