Purpose: To determine if Cobalt-Chrome (CoCr) femoral components of knee replacement components roughen significantly, and when significant roughening may start.

Methods:

Retrieval study:

14 knee replacement components were retrieved after revision procedures. The average surface roughness (Ra) of the articulating regions of each condyle was measured by surface profilometry and compared to Ra of non-articulating regions, which acted as controls on each implant.

In vitro testing:

Pin-on-plate testing of 6 paired CoCr pins and vacuum γ-irradiated UHMWPE discs was carried out under a force of 2.3kN at 1Hz to investigate how the articular Ra of CoCr pins varied with increasing number of cycles. Ra was measured at 0, 10, 100 and 1000 cycles using surface profilometry.

Results:

Retrieval analysis:

Average medial femoral condyle Ra was significantly greater than control Ra (p=0.040). Average lateral femoral condyle Ra was not significantly greater than control Ra (p=0.158). Significantly higher average Ra was seen on the medial condyles when compared with the lateral condyles (p < 0.05). 8/14 retrieved femoral components had ≥1 significantly roughened condyle (p< 0.05).

In vitro testing:

At 100 and 1000 cycles the Ra of the CoCr pins was significantly greater than Ra at 0 cycles (p< 0.05).

Conclusion: A large proportion of femoral components of knee replacement implants roughen significantly in vivo, a finding supported by our in vitro testing which indicates that roughening may begin very early on. This may have important implications for aseptic loosening of knee replacement components. However, the average Ra of those CoCr surfaces significantly (p< 0.05) roughened was within acceptable limits for orthopaedic implants (0.050μm).

The aim of surgery in the treatment of tumours of the distal radius is to achieve satisfactory clearance whilst best preserving function of the hand and wrist. Since 1992 a technique of distal radial tumour excision with reconstruction by autologous free fibula strut grafting has been employed in the treatment of thirteen patients at our unit. The procedure employs fixation of the non-vascularised fibula shaft to the proximal radius by step-cuts and a dynamic compression plate. The fibula head substitutes for the distal limit of the radius and articulates with the carpus.

We have treated 10 cases of primary or recurrent giant cell tumour and cases of osteosarcoma, chondrosarcoma and Ewings’ sarcoma by this technique. The patients were reviewed at a mean of 50 months post surgery, with assessment of their functional outcome and measurement of the range of wrist movement and grip strength.

The patient with Ewings tumour had died of meta-static disease 62 months post grafting. Three patients treated for giant cell tumour had required further surgery, two of these had forearm amputation for malignant transformation. In comparison to the unoperated wrist, range of movement was well preserved. The power of grip strength was 57% of the contralateral wrist and hand.

These results compare well with published rates of recurrence of benign giant cell tumour treated by other methods. This technique would seem to offer an acceptable functional result without compromise of the tumour prognosis.

The issue of preservation or sacrifice of the posterior cruciate ligament in total knee arthroplasty remains unresolved.

We report the results of 200 consecutive total knee arthroplasties performed at our hospital under the direction of the senior author. Pre-operatively, patients were randomly chosen to receive either a Kinemax (posterior cruciate retaining) or a Press-Fit-Condylar (posterior cruciate sacrificing) prosthesis. We implanted 97 Kinemax and 103 Press-Fit-Condylar prostheses which were prospectively followed-up by clinical and radiographic assessment. Review at mean follow-up of 2.7 years showed a satisfactory clinical result in both groups [Surace, et al., 1994].

We present the results of our further review, with maximum follow-up of over nine years (mean: 5.9 years). Revision of the implant has been performed in five knees (three Kinemax and two Press-Fit-Condylar). The polythene spacer had to be replaced in one patient with a Press-Fit-Condylar implant.

Patients were assessed with the Hospital for Special Surgery Knee Score and radiologically assessed with the Knee Society Roentgenographic Evaluation and Scoring System. Pre-operative demographics and disease states of the patients were similar, with an average Hospital for Special Surgery Knee Score of 63. At the latest assessment the average knee score was good (85). Remarkably, the mean knee score for the posterior cruciate sacrifice and the PCL groups remains similar (mean: 85). Radiographic evaluation demonstrated that the prosthetic components of both groups were in comparable alignment. The posterior cruciate ligament retained (Kinemax) patient group showed a mean 5.9 degrees of the valgus angle at the knee. The angle in the posterior cruciate ligament sacrifice (PFC implant) group was 6.2 degrees. Evaluation of the radiolucent depths below the femoral, tibial and any patella component showed a mean total depth of 1.5 mm (pcl retaining) and 1.7 mm (pcl sacrificing).

Our study presents a quantitative perspective of the results of total knee replacement with proven implant systems and performed in a general orthopaedic unit by both consultants and surgeons in training. The Kinemax (Howmedica) and Press-Fit-Condylar (DePuy Johnson and Johnson) implant systems have both previously demonstrated good results and continue to be available with little subsequent modification.

To our knowledge, there have been no other large prospectively randomised studies of posterior cruciate ligament preservation or sacrifice in total knee replacement.