Concerns recently arose regarding hip resurfacing arthroplasty (HRA), mainly referring to the metal-on-metal articulation that results in increased metal ion concentrations and that may be associated with weird soft tissue reactions. Although a number of short-term reports highlighted excellent and encouraging outcomes after HRA, mid- to long-term follow-up studies are sparse in the current literature. This study aimed to determine the five-year results of HRA using the Durom^® prosthesis in the first consecutive 50 cases. We prospectively assessed clinical and radiographic data for all patients undergoing HRA with this implant. Follow-ups were scheduled at six weeks, one year, two years and five years after surgery. All complications, revisions and failures were noted. Harris Hip Scores (HHS) and the range of motion (ROM) were determined preoperatively and at each follow-up. Oxford Hip Scores (OHS) and University of California at Los Angeles (UCLA) activity levels were determined at the last control. Comparisons were performed using paired t-tests after testing for normal distribution. The cohort comprised 13 women and 36 men (50 hips) with a mean age of 53.3 ± 10.7 years and a mean BMI of 25.9 ± 3.7 kg/m2. After a mean follow-up of 60.5 ± 2.3 months five hips had to be revised, corresponding to a resvision rate of 10%. There occurred two femoral neck fractures (after two and eleven months) and one aseptic loosening of the femoral component (after 68 months). One implant was exchanged to a conventional stem-type design due to persistent hip pain (after eight months), and one hip underwent a femoral offset correction due to a symptomatic impingement between the neck and the cup (after 29 months). There occurred no intra- or other postoperative complications. Clinically, ROM significantly improved after surgery. Hip flexion increased from 91.1 ± 15.8° to 98.9 ± 6.5° (p=0.0007), internal rotation from 5.5 ± 6.9° to 11.1 ± 8.1° (p=0.0005), external rotation from 19.2 ± 12.5° to 28.8 ± 9.1° (p=0.0001), and abduction from 27.3 ± 10.5° to 40.2 ± 11.0° (p< 0.0001). The HHS significantly increased from 55.9 ± 12.3 points to 96.5 ± 8.5 points. The OHS averaged 14.3 ± 3.0 points, and UCLA activity levels averaged 7.7 ± 1.7. The present results demonstrate that despite satisfactory clinical outcomes in terms of patient scores and ROM, the high revision rate of 10% after a mid-term follow-up is disappointing.

During the last decade, outcome assessment in orthopaedic surgery has increasingly focused on patient self-report questionnaires. The Oxford Hip and Knee Scores (OHS and OKS) were developed for the self-assessment of pain and function in patients undergoing joint replacement surgery. These scores proved to be reliable, valid, and responsive to clinical change, however, no German version of these useful measures exists. We therefore cross-culturally adapted the OHS and OKS according to the recommended forward/backward translation protocol and assessed the following metric properties of the questionnaires in 105 (OHS) and 100 (OKS) consecutive patients undergoing total hip or knee replacement in our clinic: feasibility (percentage of fully completed questionnaires), reliability (intraclass correlation coefficients (ICC) and Bland and Altman’s limits of agreement), construct validity (correlation with the Western Ontario and McMaster Universities Index (WOMAC), Harris Hip Score (HHS), Knee Society Score (KSS), Activities of Daily Living Scale (ADLS), and Short Form (SF-)12), floor and ceiling effects, and internal consistency (Cronbach’s alpha, CA). We received 96.6% (OHS) and 91.9% (OKS) fully completed questionnaires. Reliability of both questionnaires was excellent (ICC > 0.90). Bland and Altman’s limits of agreement revealed no significant bias. Correlation coefficients with the other questionnaires ranged from −0.30 (SF-12 Mental Component Scale) to 0.82 (WOMAC) for the OHS, and from −0.22 (SF-12 Mental Component Scale) to −0.77 (ADLS) for the OKS. For both questionnaires, we observed no floor or ceiling effects. The internal consistency was good with a CA of 0.87 for the OHS and 0.83 for the OKS. In conclusion, the German versions of the OHS and OKS are reliable and valid questionnaires for the self-assessment of pain and function in German-speaking patients with hip or knee osteoarthritis. Considering the present results and the brevity of the measures, we recommend their use in the clinical routine.

Introduction: Cementless press-fit cups are the most widely used acetabular implants in total hip arthroplasty today. Their primary and secondary stability is largely determined by the design and choice of surface coating. Porous titanium coatings are used for the majority of cementless acetabular implants. However, an additional hydroxyapatite (HA) layer has been advocated for superior bone ongrowth. We studied the effect of additional HA coating on early micromotion of a porous titanium plasmasprayed cup with a flattened pole. A secondary objective was to compare the extent of micromotion of this well established cementless cup to data of other press-fit cups.

Methods: A total of 44 female patients (45 hips) undergoing total hip arthroplasty for osteoarthritis consented to participate in this prospective, IRB approved study. They were randomized for either a press-fit cup (EP-FIT PLUS^®, Plus Orthopedics AG, Switzerland) with a titanium plasma sprayed surface (Ti-group) or with additional HA coating (HA -group). All cups were used with the same combination of stem, PE liner and ceramic head. Model-based radiostereometry (MBRSA) was used to measure translation and rotation immediately postoperative, at 6 weeks, 3, 6, and 12 months. Statistical analysis of migration was performed utilizing one-sided Mann-Whitney tests and ANOVA.

Results: At one year, mean translation in the HA-group (Ti-group) along the medial-lateral (x), proximal-distal (y) and anterior-posterior (z) axes was −0.01 (0.07), 0.08 (0.09), and 0.03 (−0.06) mm, respectively. Mean rotation around the x-axis (anterior-posterior tilt) was −0.19 (−0.16), the y-axis (anteversion-retroversion) was −0.10 (−0.19), and the zaxis (adduction-abduction) was 0.23 (−0.05) degrees. Our hypothesis that translation and rotation would be different in the two groups was rejected (p< 0.00) for all dimensions except for rotation about the z-axis (p=0.10). The was no evidence for different migration patterns throughout the examined time points. All patients had excellent clinical outcome with a mean Harris Hip Score of 95.4 (HA-group) and 95.3 (Ti-group) (p=0.10). Plain radiographs of the cups showed good osseointegration.

Discussion: With excellent primary stability in both the Ti-group and the HA-group, we conclude, that HA-coating does not significantly increase stability of this flattened pole press-fit cup during the first postoperative year. We were able to show that the early stability of this cup is well comparable to that of the more frequently used hemispherical cups with initial stability being one prerequisite for long-term success. RSA measurements after 2 years will be conducted to confirm the current findings and the cup is also being studied in a long-term observation.

Introduction: Rotational alignment of the femoral component is widely believed to be crucial for the ultimate success of total knee arthroplasty (TKA). However there is a paucity of normative data on femoral component rotation in ‘perfect’ TKA.

Methods: Femoral component rotation in well-functioning TKA was assessed by means of axial radiography as described by Kanekasu et al. Well-functioning TKA were defined by three criteria at 5-year follow-up:

Knee Society objective and functional score of 190 or above

Thirty TKA of 29 patients (9 male, 20 female) with a median age of 70 years (range, 31–87) at time of surgery fulfilled the study criteria. All TKA were implanted at a single high-volume joint replacement center in 2002. In all cases both the condylar twist angle (CTA) using the clinical epicondylar axis (CEA) and the posterior condylar angle (PCA) using the surgical epicondylar axis (SEA) were used to assess rotational alignment of the femoral component.

Results: Overall, the mean CTA was 3.6+−3.5° of internal rotation (IR) (range, 4.1° of external rotation (ER) to 8.6° of IR) for the femoral component. For females, the CTA had a mean value of 4 +/−3.7° of IR (range, 7.6° of IR to 4.1° of ER) compared to 2.3 +/−3° of IR (range, 5.3° of IR to 2.5° of ER) in males. Overall, the mean PCA was 1.5 +/−3.5° of ER (range, 8.4° of ER to 5.1° of IR). In females, the mean PCA was 1 +/−3.9° ER (range, 2.3° of IR to 5.8° of ER) compared to 2.8 +/−2° ER (range, 0.4° of ER to 5.7° of ER) in males. The mean angle between CEA and SEA was overall 5.1 +/−1.8° (range, 3.3° to 9.1°), in females 5.1 +/−1.6° (range, 3.5° to 9.0°) compared to 5.0 +/−2.4° (range, 3.2° to 9.1°) in males.

Conclusion: Well-functioning TKA demonstrated a highly variable rotational alignment of the femoral component ranging from excessive external rotation to excessive internal rotation. These findings challenge current reference values for optimal femoral component rotation.

Introduction: Since the introduction of the Zimmer Innex UCOR (Ultra COgruent Rotating) mobile bearing total knee arthroplasty (TKA) system in 1999, there were close to 3000 primary TKAs performed at our institution utilizing this implant. We report on the first 396 5-year follow-up results and overall revisions in our total collective.

Methods: Between 1999 and 2006 there were 2734 primary Innex UCOR TKA performed (1748 female/987 male) at the Schulthess Clinic, Zurich. Primary diagnosis leading to TKA were OA (2462 – 90%), RA (144 – 5.3%), posttraumatic arthritis (65, 2.4%), necrosis (50, 1.8%) and misc causes (13 – 0.5%). The mean age of the females patients was 69y (33y – 92y), and 68y (31y – 93y) in the male population. To date 396 knees underwent clinical and radiological follow-up at 5 years (mean 5y 0m, range 4y 1m – 7y 2m), with 5% of the patients being lost to follow-up. Scoring was done, using the Knee Society Score (KSS). All patients had a full leg radiograph pre-operatively as well as at follow-up.

Results: Total KSS improved from 106.5 (6 – 184) pre-operatively to 179.5 (80 – 200) at follow-up, the knee score from 42.2 (2–93) to 92.1 (37 – 100), the function score from 64.3 (0–100) to 87.4 (10–100) respectively. The pain score increased from 17.7 (0–50) to 47.5 (20–50, 50 points maximum). ROM pre-operatively was 104.6° (0–145) and reached 117.2° at follow-up (55–145). Subjective evaluation by the patient at 5 years was excellent and good in 91%, fair in 8% and taxed poor by 1% of the patients. 95% of full leg radiographs showed a femorotibial angle of 182°–188°, 3% were < 182° (varus), 2% > 188° (valgus). Overall revision rate (95 of 2735) was 3.5%, 1.1% for infections and 1% for anterior knee pain and/or patella pathology. 0.6% were revised for instability, 0.3% for arthrofibrosis, and the remaining 0.5% for various problems.

Conclusion: These promising 5 year observations with the Innex UCOR mobile bearing TKA system suggest favorable overall midterm results. Further longer term follow-up evaluations are scheduled while 5 year follow-ups are ongoing, allowing for continuing reports on long-term performance.

Introduction: Stiffness after primary total knee arthroplasty (TKA) is a severe complication that has been associated with excessive internal rotation of the femoral component.

Methods: Between 2001 and 2004, 18 patients with 18 well-fixed, aseptic primary TKA underwent revision TKA at a single high-volume joint replacement center for stiffness in the presence of femoral component mal-rotation. Stiffness was defined as ROM with less than 90° of maximum flexion or a flexion contracture greater than 10°. Femoral component malrotation was defined as a condylar twist angle of more than 4° of internal rotation using CT scans. Following IRB approval, 17 out of 18 patients (median age at time of the index surgery 62.7 years, range 45 to 78; female, n=11; male, n=6) were available for retrospective outcome assessment. The mean time between primary and revision TKA was 3.2 years (range, 9–79 months). At a mean follow-up of 3.3 years (range, 2 to 6), all patients were evaluated clinically using the Knee Society objective and functional scores, and by CT measurement of femoral component rotation. Patients without additional procedures between primary and index revision TKA (group A, n=9) were compared using Student t-testing with those which had undergone additional interventions (group B, n=8).

Results: Five patients had required additional procedures after the index revision TKA including closed manipulation under anesthesia in one case, patellar resurfacing in one case, metal removal after tubercle osteotomy and open debridement in another case, and tibial component revision followed by revision TKA in one case. CT scans after revision TKA revealed correction of femoral component rotation in all but one case from each group. After revision TKA, the mean objective score was overall 73 points, in group A 82 points compared to 63 points in group B (p< 0.001). In group A there were 78% excellent or good results compared to 13% in group B. The mean function score was overall 74 points, 78 points in group A compared to 69 points in group B. There were 67% good or excellent results in group A compared to 12% in group B. Mean flex-ion increased overall from 71 to 92 degrees (p< 0.01), in group A from 61 to 96 degrees (p< 0.01) and in group B from 82 to 89 degrees. Mean flexion contracture was reduced overall from 7 to 4 degrees, in group A from 6 to 3 degrees, and in group B from 8 to 5 degrees. Stiffness persisted in four cases (24%) (group A, n=1; group B, n=3). Satisfaction (VAS 0–100; 100=completely satis-fied) scored overall a mean of 52 points, in group A 57 points and in group B 44 points.

Conclusion: Overall, revision TKA for knee stiffness associated with femoral component internal malrotation resulted in significantly improved knee motion. However, outcome was less predictable in those patients with additional procedures between primary and revision TKA.

Introduction: Resurfacing arthroplasty is rapidly gaining popularity, the patients are in many cases very satisfied with the result. However some patients continue to complain about persistent groin pain, which is not clearly understood and attruibuted to different causes.

We identified femoro-acetabular impingement as a source of pain, which promptly disappeared after surgical off-set restoration.

Method: Since 2002 we implanted 390 hip resurfacing systems. At a one-year follow-up 16 patients complained about groin pain, especially when starting to walk.

In 6 patients the clinical examination and the rx could demonstrate femoro-acetabular impingement. In four cases this was due to anterior osteophytes of the femoral neck, in two cases it was due to retroversion of the femoral implant. These 6 patients were revised.

Results: During surgery femoro-acetabular impingement between these osteophytes on the femoral neck and the acetabular rim or the implant could be demonstrated. The head-neck off-set was restored with a high-speed burr. Interestingly rapid bleeding of the femoral neck was noted in all cases confirming the presence of vital bone. After surgery five of the six patients were painfree after 6–12 weeks. One patient did not experience a difference until now. There were no femoral neck fractures seen after this procedure.

Conclusion: Femoro-acetabular impingement seems to be a common source of persistent groin pain after hip resurfacing. Care has to be taken to restore the head-neck offset during implantation.

Patella management in total knee arthroplasty remains controversial. Minimizing patella related problems is the main goal in any type of knee arthroplasty. This can be achieved with and without resurfacing. However, patella resurfacing resulted in, at times, catastrophic failures, which increased the popularity of patella non resurfacing, particularly with anatomical femoral groove designs. If patella non resurfacing is to be recommended, clinical outcomes must be equal or better than those of routine patella resurfacing in the specific prosthesis utilized.

From a large cohort of over 6000 TKA five studies were conducted to analyze isokinetic strength, subjective, clinical, and radiographic outcomes as well as histopathological data.

Isokinetic strength, subjective, clinical, and radiographic outcomes favor nonresurfacing in TKA with proper femoral component rotation and conforming patellar groove. Our data indicate that patella subluxation and femoral component malrotation is significantly associated with development of arthrofibrosis.

On the base of our studies we propose specific surgical techniques for optimal patella treatment (patelloplasty) in TKA.

Patellectomized knees often perform poorly with respect to extensor mechanism function. Reconstruction options and literature reports are limited. The purpose of this study was to describe and review bone graft patella reconstruction in TKA.

Material_e_Methods: Since 1990 nine previously patel-lectomized patients underwent cementless Low-Contact-Stress TKA with autologous patella reconstruction. One patient died 5 years post surgery. Mean follow-up was 8.0 years (6 to 12). Autologous bonegraft was taken in five cases from the iliac crest, in two cases from the posterior femoral condyle and in two cases from the opposite patella at time of simultaneous bilateral TKA. Postoperative evaluation included clinical and radiographic analysis and bilateral comparative isokinetic strength measurement at 60 degrees per second (Biodex).

Clinical scores had a mean of 27 points (max: 30) and mean isokinetic extension strength of 71Nm (81 percent) compared with the opposite healthy patella site. One patient with bilateral patellectomy and unilateral patella reconstruction showed a 50 percent increase of strength on the grafted side. Radiographs showed minor signs of neopatella bone resorption, but a maintained leaver arm.

Reconstruction of a neo-patella in TKA with autograft provides marked improvement of isokinetic extensor strength, little evidence of autograft resorption, excellent or good clinical outcome and high patients satisfaction after a mean of 8 years. The results of this study indicate encouraging data for reconstructing a new patella and lever arm in patellectomized knees during primary or revision TKA. Cosmetic improvement in females is another subjective advantage.

The purpose of this prospective and randomized study was to objectively evaluate isokinetic strength, clinical, and radiographical outcome in bilateral TKA using the same prosthesis with and without patella resurfacing.

Bilateral TKA, one with, one without patella resurfacing was performed in 22 osteoarthritic patients, mean age was 68 years using the Low-Contact-Stress prosthesis. Minimum Follow-up was one year. Evaluation included clinical investigation, specific patella scores, radiographic analysis and isokinetic strength measurement of both knee flexion and extension at 60 degrees per second (Biodex). surement at 60 degrees per second (Biodex).

There was no significant clinical score difference, but mean isokinetic strength of knee extension was significantly (p< .0001) stronger in the non-resurfaced patella TKA (40.5 Nm) compared with the resurfaced TKA (38,5 Nm). Flexion was also significantly stronger in the patella non-resurfaced group with 22.4 Nm versus 19.5 Nm in the resurfaced group. Mean lateral deviation was significantly (p< .001) less ideal in the resurfaced group as was postoperative patellofemoral congruent contact (p< .001). However, there was no correlation between lateral patella deviation or congruent contact and iso-kinetic strength.

The results of this study indicate that mean isokinetic strength of both knee flexion and extension was significantly stronger in the non-resurfaced patella TKA. This study provides encouraging data for patella non-resurfacing. However, clinical scores or patient’s preference did not show any difference.

The purpose of this study was to determine whether internal mal-rotation of the femoral component is associated with arthrofibrosis in TKA. Multiple etiological factors have been suggested, but specific causes have not been identified. We hypothesized arthrofibrosis may be triggered by a combination of non-physiological kinematics (femoral component internal rotation) and a tight medial compartment.

From a consecutive cohort of 3058 mobile bearing TKA forty-four (1.4%) cases were diagnosed as having arthrofibrosis, of which thirty-eight (86%) cases could be recruited. Thirty-eight patients with a well functioning TKA served as matched controls. Evaluation included CT investigation to determine femoral component rotation with reference to the transepicondylar axis (TEA).

Results: Femoral components in the AF group were significantly (p< 0.00001) internally mal-rotated by a mean of 4.7 degrees ranging from ten degrees internal rotation (IR) to one degree external rotation (ER). Mean femoral rotational in the control group was parallel (0.3 degrees IR) to the TEA (six degrees IR to four degrees ER). Arthrofibrosis was not associated with age, gender, body-mass-index, or preoperative diagnosis

There is a highly significant association between arthrofibrosis in TKA and internal mal-rotation of the femoral component. On the base of these results it was hypothesized that non-physiological kinematics in TKA with mal-aligned femoral components influence and/or trigger arthrofibrosis in TKA.

Aims: The purpose of this study was to evaluate the clinical outcome of 457 LCS mobile bearing TKA from one centre.

Methods: From a cohort of over 3.500 mobile bearing TKA in one large center, 457 cases were performed more than 10 years ago (mean 11 years). Drop-out were 63 (13.8%) cases, 128 patients were known to have died and 63 (13.2%) cases could not be included leaving 86.2% that entered the study. Patient demographics included 76% females and 8% rheumatoids. There were 275 (60%) meniscal bearing and 182 rotating platform design components. The patella was resurfaced in 95 (21%) cases.

Results: Preoperative KSS scores improved from a mean of 84 to 157 points and mean range of motion from 97 to 110 degrees postoperatively. Clinical scores were excellent or good in 88%, fair in 10% and poor in 2%. Kaplan Meier survival analysis was 96.9% after a mean of 11 years taking any revision into account. Worst track records were polyethylene meniscal bearings with 91.2% and best the femoral component with 99.8% after a mean of 11 years. Other complications will be listed in depth.

Conclusion: Best track record was noted with the all cruciate sacrificing rotating bearing device and worst with the ACL and PCL retaining meniscal bearing device. Patella also jeopardized the long-term results.

Aims: The purpose of this study was to determine whether internal mal-rotation of the femoral component is associated with arthrofibrosis in TKA. We hypothesized arthrofibrosis may be triggered by a combination of non-physiological kinematics (femoral component internal rotation) and a tight medial compartment.

Methods: From a consecutive cohort of 3058 mobile bearing TKA forty-four (1.4%) cases were diagnosed as having arthrofibrosis, of which thirty-eight (86%) cases could be recruited. Thirty-eight patients with a well functioning TKA served as matched controls. Evaluation included CT investigation to determine femoral component rotation with reference to the transepicon-dylar axis (TEA).

Results: Femoral components in the AF group were significantly (p< 0.00001) internally mal-rotated by a mean of 4.7 degrees ranging from ten degrees internal rotation (IR) to one degree external rotation (ER). Mean femoral rotational in the control group was parallel (0.3 degrees IR) to the TEA (six degrees IR to four degrees ER). Arthrofibrosis was not associated with age, gender, body-mass-index, or preoperative diagnosis.

Conclusions: There is a highly significant association between arthrofibrosis in TKA and internal mal-rotation of the femoral component. On the base of these results it was hypothesized that non-physiological kinematics in TKA with mal-aligned femoral components influence and/or trigger arthrofibrosis in TKA. In TKA with arthrofibrosis, we now consider femoral CT evaluation with the view to surgically rebalancing the flexion gap and realigning the femoral component, when internal mal-rotation is confirmed.

Aims: Patellectomized knees perform poorly with respect to extensor mechanism function and anterior knee pain.

Methods: In the period of 1990 to 1995, nine previously patellectomized patients with a mean age of 55 years (range: 38 to 67) underwent cementless Low-Contact-Stress TKA with autologous reconstruction of a new patella. One patient deceased 5 years post surgery. Mean follow-up was 8.0 years (range: 6 to 12) The autograft was taken in five cases from the iliac crest, in two cases from the posterior femoral condyle and in another two cases from the opposite patella at time of simultaneous bilateral TKA surgery. Evaluation included clinical investigation, specific patella score, radiographic analysis and isokinetic strength measurement at 60 degrees per second (Biodex).

Results: Clinical scores had a mean of 27 out of 30 points (range: 19 to 30) and mean isokinetic strength of knee extension reached 71Nm (81%) compared with the opposite site. One patient with bilateral patellectomy and unilateral TKA showed an increase of 50 % strength (51Nm versus 77Nm) in the knee with TKA and neo-patella. Radiographs in three planes showed minor signs of neo-patella bone resorption in three cases, but evidence of retrabeculation and bone remodelling in all neo-patellae.

Conclusions: Reconstruction of a neo-patella in TKA using autograft provides near to normal isokinetic strength, no evidence of considerable autograft resorption, excellent or good clinical outcome and high patients satisfaction after a mean of 8 years. The study provides encouraging data for reconstructing a new patella in patellectomized knees during TKA.

Introduction: The standard implant for patients with rheumatoid arthritis is a cemented system. Early aseptic loosening is a major concern in patients with bad bone quality, usually seen in inflammatory arthritis

Aim of the study: The aim of this retrospective study is to find out, whether the cementless CLS-stem is an appropriate implant for patients with rheumatoid or juvenile arthritis.

Material and methods: Between 1984 and 2002 63 patients with rheumatoid or juvenile arthritis were treated with a cementless Stem (CLS) in our clinic. The mean age was 53 years (range from 25 to 71 years). We evaluated the x-rays (aseptic loosening and other complications) as well as the clinical outcome (Harris Hip Score). Patients with a minimum follow-up of 24 months (mean fu 5 years) were included in the study.

Results: There was no stem revision due to aseptic loosening. No patient had radiological signs of aseptic loosening. 8 patients suffered a fracture of the greater trochanter or the proximal femur during surgery. Two patients had to be revised for trochanteric problems.

Conclusion: The cementless CLS stem is an appropriate implant for patients with rheumatoid or juvenile arthritis. Careful implantation is necessary to avoid trochanteric or femoral fractures.

Accepted landmarks for determining rotation include the posterior condyles, Whiteside’s line, arbitrary 3-4° of external rotation, and transepicondylar axis (TEA). All methods require anatomical identification, which may be variable.

The purpose of this study was to radiologically evaluate femoral component rotation (CT analysis) based on a method that references to the tibial axis and balanced flexion-tension.

Methods: CT scans of 38 randomly selected TKA were evaluated to determine femoral component positioning. Spiral CT scans of the femoral epicondylar region with eight 4mm cuts were performed to accurately identify medial and lateral epicondyles. Rotational alignment was measured in relation to the transepicondylar axis using CT-implemented software by two independent radiologists.

Results: Femoral component rotation ranged from 4° internal rotation to 5° external rotation with a mean of 0.0° = parallel to the TEA. All 38 cases had satisfactory clinical results, range of motion of over 90°, and showed perfect patello-femoral tracking and patellar congruency.

Conclusions: Femoral rotation position based on tibial axis and balanced flexion tension is patient specific, reproducible and results in predictable patella tracking. CT analysis in this study confirms that the tibial axis method produces a consistent femoral component positioning that relates accurately to the TEA. Tibial axis method avoids the need for arbitrary landmark identification, placing the femoral component predictably in an optimum position in relation to the tibia and patella.

The low contact stress and self-aligning properties of mobile bearing total knee replacements (TKR) make them an increasingly popular implant choice worldwide. Two variations on the mobile bearing knee concept have been commonly adopted: systems that retain the posterior cruciate ligament (PCL) and provide free rotation and translation (RT) of the mobile bearing, and systems that sacrifice the PCL and provide for rotation only (RO) motion of the mobile bearing. The purpose of this study was to evaluate the in vivo kinematics of these two types of mobile bearing TKR during gait, stair, and two deep knee flexion activities.

Twelve patients (6 RT, 6 RO) with unilateral mobile bearing knee arthroplasty and excellent functional outcomes at least one year after TKR were studied. Fluoroscopic images of the knee were acquired as patients walked on a treadmill, ascended a step, performed a deep knee bend, and knelt to maximum flexion. Knee kinematics were derived from CAD model based shape matching techniques.

The RT knees exhibited greater posterior translation of the femur on the tibia during early stance in gait (RT: 5mm vs. RO: 2mm) and during knee extension during stair ascent (RT: 5mm vs. RO: 1.5mm). There were no differences between the two groups in the flexion angles achieved during deep knee bend or kneeling.

Although there were no significant clinical or functional differences in these patients, the RO knees exhibited smaller tibio-femoral translations and less intersubject variability in knee kinematics during dynamic weight-bearing activities.

The purpose of this study was to analyse and to recommend solutions for early complications with a new total knee mobile bearing device, that promises a logical synthesis of combined A/P translation and rotation ability, but has shown early surgical technique related complications.

Materials and Methods: There were 244 Low Contact Stress (LCS) A/P glide total knee replacements (TKA) performed in the time between 1995 and 1999. Mean age was 67.2 years (range: 53-83). Mean follow-up was 16.5 months (range: 1-51). There was an unusual high incidence of anterior knee pain in this group compared with excellent results utilising rotating platform LCS TKA in this centre. Diagnostic evaluation included radiographs, arthroscopical evaluation, and positron emission tomography in five selected cases.

Results: There were 11 (4.5%) cases with Hoffa fatpad impingement, progressive ligament instability in 5 (2.0%) cases, arthrofibrosis in 4 (1.6%) cases, one malposition of tibial component, and one proximal tibial AVN. Five PET 18F-FDG scans prior to revision surgery revealed increased up-take correlated with intraoperative findings of fatpad fibrosis and/or necrosis.

Conclusion: The LCS A/P glide mobile bearing TKA has theoretical advantages over both meniscal and rotating mobile bearing knee designs. Early occurrence of Hoffa fatpad impingement was caused by surgical mal-technique in this centre that usually retains the vast majority of the fat pad. Revision surgery revealed evidence of impingement and all cases revealed clinical improved after partial excision of the fatpad. We, therefore, recommend partial to total excision of the Hoffa fat pad for utilisation of the A/P glide prosthesis.

The purpose of this study was to analyse a potential correlation of arthrofibrosis (AF) and femoral rotational mal-alignment in total knee arthroplasty (TKA). We hypothesized an increased internal mal-rotation of the femoral component leading to unphysiological kinematic motion of the arthroplastic knee joint. These repetitive microtrauma may then induce increased synovial hyperplasia leading to arthrofibrosis. Arthrofibrosis is an ill-defined entity that results in unsatisfactory outcome following TKA. Biological and mechanical factors have been suggested as etiology, but specific causes have not been identified.

Methods: From a cohort of 3058 mobile bearing TKA 44 (1.4%) cases were diagnosed with arthrofibrosis, of which 38 (86%) cases underwent clinical examination and CT investigation to determine femoral component rotation taking the transepicondylar (TEA) axis as reference point. A control group with 38 well functioning TKA was compared.

Results: Increased internal mal-rotation of the femoral component of 5.0° in the AF group (reference to the TEA) was highly significant (p < 0.001) ranging from 10°IR to 1°ER compared with the control group (0.0° parallel to TEA, 4°IR to 5°ER). Men younger than average for index TKA in this center with a decreased BMI, previous knee surgery (particularly correcting osteoto-mies), poliomyelitis, and OA had an increased risk of developing arthrofibrosis. PCL retaining or sacrificing, patella resurfacing or retaining had no increased prevalence for AF. Rheumatoid patients had a decreased risk of developing arthrofibrosis .

Conclusion: The correlation of AF to femoral component internal mal-rotation was statistically significant (p < 0.001). These results confirm that unphysiological kinematics in TKA appear to be a major etiopathological factor for arthrofibrosis (AF). In this study femoral component internal mal-rotation has shown to be a significant risk factor in the development of arthrofibrosis. We, therefore, recommend consideration of early CT evaluation in cases with AF and, when internally mal-rotated, revision of the femoral component.

This study has been cleared by the Ethical Committee, University of Zurich, Switzerland.

Correction of fixed valgus is a challenge in primary TKA. Achieving patello-femoral and femoral-tibial stability requires superficial/deep lateral side releases if non-constrained prostheses are utilized. The medial approach has disadvantages with more reported complications. The direct lateral approach, with/without tubercle osteotomy, is an approach option utilized in two reporting centers.

Methods: 255 valgus TKAs with 5- to15-year follow-up were reviewed. Demographics included 91% females, 15% rheumatoid, mean age 69. Prostheses utilized were LCS mobile-bearing (meniscal PCL-retaining/rotating PCL-sacrificing). Patella was non-resurfaced in 90%; cementless fixation in 86%. The direct lateral approach with similar lengthening techniques was used with tubercle osteotomy in one center and osteo-periosteal joint exposure in another.

Results: Good/excellent 91%, modified HSS score improvement 57 to 85. Deformity (12) improved < 8 to 12 points (> 15o valgus to < 5o valgus). ROM improved from mean 11o/97o to 1/110o latest. Technical/prosthetic-related complications included: 7 bearing failures (5 meniscal, 2 rotating platform), 2 aseptic loosenings (tibial), 1 patella ligament rupture and 2 screw loosenings in the osteotomy group, 1 patella re-dislocation in a 75-year-old female with dislocation since age 15 (non-osteotomy group), 2 infections, and 1 re-operation for arthrofibrosis .

Discussion/Conclusion: Valgus TKA using LCS move-able bearings implanted via a direct lateral approach are highly successful regarding stability and patella tracking. Failures correlate with inadequate/de-stabilizing releases and meniscal PCL-retaining prostheses. Rotating bearings allow for better stability and self-adjustment of common mal-rotation variables. The lateral approach allows for direct (step-wise) lengthening releases, improved patellar tracking, and precise gap balancing.