Malpositioning of prosthetic components in TKA may cause clinical relevant complications. This study focuses on a variety of TKA problems that were related to femoral component internal malrotation.

Inclusion criteria in this study were all TKA seen at one-year follow-up with a moderate or poor clinical outcome using the Knee Society Score. Reduced mobility, pain, and patella problems were most frequent in this group. Infection, trauma, or wound problems were exclusion criteria. Two different mobile bearing knee systems were utilised in one large centre; LCS (DePuy Int, Leeds, UK) and MBK (Zimmer, Warsaw, USA). From more than 200 LCS and 70 MBK prostheses 27 cases entered the study, all of which underwent spiral CT investigation for evaluation of femoral component rotational alignment.

There was an increased incidence of femoral component internal rotation in this group with poor outcome. Mean internal rotation was 4.2 degrees (0 to 8) in relation to the transepicondylar axis.

Evaluation of femoral component rotational alignment in TKA has recently gained increased attention. Particularly internal malrotation does often lead to flexion instability, poor biomechanics, and patellofemoral tracking problems with lateral subluxation. It is also associated with painful and stiff knees as recently reported (AAOS 2002, Dallas, USA). In this study early postoperative complications in TKA were also associated with femoral component internal malrotation. We, therefore, recommend CT evaluation of component alignment in clinically doubtful knees. Cases that present with internal malrotation should be considered for revision surgery with the view to revise the femoral and/or tibial component.

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.