LIVRE JDG 2014

S. Lustig, C. Scholes, S. Oussedik, M. Coolican, D. Parker

The hip was taken through a range of motion

and a digital hip centre generated by the

software package. A midline knee incision was

then performed, prior to a medial parapatellar

arthrotomy. The medial collateral ligament was

elevated from the tibia sufficient to gain access

to the joint. Registration of the epicondyles,

femoral centre, AP axis and femoral condyles

was then undertaken with the navigation

system, followed by registration of tibial

landmarks and malleoli. The lateral epicondyle

was defined as the most lateral prominence of

the lateral femoral condyle, whilst the medial

epicondyle was defined by the medial sulcus of

the medial epicondyle. The navigation software

then generated the surgical trans-epicondylar

axis, a line connecting the 2 epicondyles.

The PSCB was used in accordance with the

manufacturer’s instructions, with careful

positioning over the articular surfaces. The

accuracy with which the PSCB conformed to

the articular surface was checked by an observer

from Smith and Nephew, ensuring the PSCB

was used in the recommended fashion. Drill

holes and pins in the tibial and femoral

periarticular bone were placed through the

respective PSCB to determine the orientation

of the standard cutting guides, which were

recorded with the navigation system (fig. 1)

[2]. The parameters assessed intraoperatively

included the PSCB alignment and depth for

both the femoral (coronal, sagittal, rotational)

and tibial cuts. In addition, agreement between

the planned sizing for the tibial and femoral

components and the sizing determined

intraoperatively was recorded (Table 1).

The PSCB-defined bone cuts were only used if

the intra-operative measurements confirmed

acceptable alignment, which was defined as

within ±2° or ±1mm of the pre-operative plan

in each plane. If this was not achieved, the

PSCB was removed and the procedure was

performed with the navigation system in a

standard manner.

Fig. 1 : Intraoperative view of PSCB positioning for the femur (A)

and assessment of alignment with the navigation system (B).

General

Femoral PSCB

Tibial PSCB

Fit

Sizing

Conformity

Coronal alignment

Limb alignment

Sagittal alignment

Rotation

Cut depth

Table 1: Parameters assessed intraoperatively.