Aims: To evaluate different surgical techniques of lateral meniscal allograft transplantation in cadaver knees, and to assess how these techniques affect tibial contact pressures.

Methods: The femoral and tibial shafts of five human cadaver knees were cemented into steel pots. Fresh-frozen irradiated human meniscal allografts were supplied by the East Anglia Tissue Services Department of the National Blood Service.

The knees were mounted into an Instron materials testing machine. Paddles of pressure-sensitive Fuji Prescale Film were inserted into the lateral compartment of the knee, underneath the lateral meniscus. Each knee was then loaded to 700N for 10 seconds. The Fuji Film paddles were digitally scanned and then analysed using Scion Image Analysis software to determine the intra-articular contact pressures.

Contact pressures were then determined after (i) total lateral meniscectomy, (ii) lateral meniscal allograft transplantation using a bone plug-keyhole technique to secure the horn attachments, and (iii) after insertion of the graft by suturing only.

Results: Total lateral meniscectomy led to a mean increase in maximum contact pressures of 103% (s.d. 63). Mean maximum contact pressures after lateral meniscal transplantation with a bone cylinder were 59% (s.d. 60) greater than the intact state, and after suturing only of the graft, were 85% (s.d. 74) greater than the intact knees.

Conclusions: Overall, lateral meniscal transplantation did partially restore contact pressures within the knees, and the use of a graft attached to a bone cylinder appeared to be more effective than just simple suturing of the graft. However, the results varied greatly between the different knees. In two knees, the results of meniscal transplantation were excellent. However, results were poor in knees with inaccurate graft-to-host size matching or where there was significant articular degeneration.

Introduction: Accurate size-matching of meniscal allografts is essential to maintain tibiofemoral congruity, and therefore function, especially when the surgical technique of using a bony bridge is employed.

Methods of accurately assessing the required dimensions of an ideal meniscal allograft for each patient are limited. One popular method used is to choose the appropriate graft according to the bony tibial plateau dimensions of the patient, as determined from plain radiographs.

Aims: To correlate meniscal dimensions with the bony dimensions of donor tibial plateaus.

Methods: 22 left and right pairs of donor tibial plateaus with intact meniscal allografts were obtained, giving a total of 88 individual meniscal allografts. Using a digital micrometer, the following meniscal dimensions were measured: anteroposterior length, medial-lateral width, and the radial width at the mid-point of the meniscal body. Peripheral circumference was measured using flexible steel wire. Medial and lateral bony tibial plateau width and length, and total plateau width were also recorded.

Linear regression analysis was used to obtain a formula, relating each meniscal dimension to the various bony plateau measurements. The resulting equations were used to calculate an expected meniscal dimension from the measured plateau dimensions, and this was compared to the size of the actual dimension measured.

Results: The magnitude of the meniscal dimensions measured approximately fitted a normal distribution amongst all the specimens studied. The tibial plateau widths ranged from 69.2mm to 88.4mm (mean 78.5mm, s.d. 5.4mm), a 28% difference. The mean difference between meniscal measurements between the left and right knee of each pair was 7.3%. However, the greatest individual difference observed was 41.8%.

The mean percentage error between meniscal dimensions calculated from specific compartmental tibial plateau dimensions, and the actual measured meniscal dimensions was 5.3% (s.d. 4.1%). When using just total bony tibial plateau width to calculate meniscal dimensions, the percentage error was 6.2% (s.d. 4.9%). This difference was not statistically significant. The maximum error between calculated and actual meniscal dimensions was 32%.

Conclusions: This anatomical study shows that the use of plateau dimensions as a determinant for the sizing of meniscal allografts can be used to predict meniscal dimensions. However, mean errors are in the region of 5% – 6%, and can be as high as 32%. The potential mechanical effects of such graft to host size mismatching must be carefully borne in mind.