Aims: To determine load to failure for four different meniscal repair techniques, and to assess gapping across repairs under cyclical loading.

Background: Studies comparing the biomechanical properties of different meniscal repair systems are limited, and most have simply investigated load to failure. Meniscal tissue is highly anisotropic, and far weaker under tension in the radial direction. Load to failure using high loads may, therefore, not be the most physiologically relevant in-vitro test for repair of circumferential tears, and measuring increases in gapping across repair sites under cyclical loading at lower loads may be of greater importance.

Methods: Bovine menisci were divided vertically, 5mm from the peripheral edge to simulate a circumferential tear, and then repaired using one to four techniques: vertical loop sutures using 1 -PDS, bioabsorbable Meniscal Arrows (Atlantech), Meniscal Fasteners (Mitek) or T-Fix Suture Bars (Acufex). Nine specimens were tested in each group using an Instron 5500 materials testing machine to determine load to failure. A further nine specimens in each group were tested by cyclic loading between 5N and 10N at 20mm/min for 25 cycles, using a digital micrometer to measure initial gapping, and a Differential Variable Reluctance Transducer to measure the progressive increase in gapping across the repair site during the cyclical loading. Data was analysed by ANOVA and Tukey’s multiple comparison post test using Prism (GraphPad) software.

Results: The mean loads to failure (with s.d.) in Newtons were: Sutures 72.7 (22.0), Arrows 34.2 (15.4), Fasteners 40.8 (13.4), and T-Fix 49.1 (13.8). The load to failure was significantly greater with the Sutures compared to the Arrows (p< 0.001), the Fasteners (p< 0.001) or the T-Fix (p< 0.05).

The mean gapping across the repairs after 25 load cycles (with s.d.) in millimetres was: Sutures 3.3 (1.0), Arrows 2.2 (0.9), Fasteners 4.0 (0.6) and TFix 3.5 (0.7). The mean gapping was significantly less for the Arrows compared to the Sutures (p< 0.05), the Fasteners (p< 0.01), or the T-Fix (p< 0.05).

Conclusions: These results confirm that meniscal repair by suturing gives the highest load to failure, but show that Arrows give superior hold with the least increase in gapping across a repair under cyclical loading by this test protocol.

Objective: To provide a functional, anatomical description of the posteromedial structures, allowing future biomechanical studies to evaluate how they act to restrain tibio-femoral joint motion and contribute to joint stability.

Methods: Twenty fresh cadaveric knee joints were dissected. The appearance of the medial ligament complex was recorded using still and video digital photography as the specimens were flexed, extended, internally and externally rotated.

Results: We divided the medial structures into thirds, from anterior to posterior, and into three layers from superficial to deep: Layer 1: Fascia. Layer 2: Superficial MCL. Layer 3: Deep MCL and capsule. In the Posteromedial Corner (posterior third) it is not possible to separate Layers 2 and 3. The posteromedial corner (PMC) envelops the posterior medial femoral condyle. A discrete posterior oblique ligament (POL) is not identifiable. The PMC appears to be a functional unit with a role in passively restraining tibio-femoral valgus and internal rotation with the knee extended. The semimembranosus, through its tendon sheath attachments, may act as a dynamic stabiliser.

Conclusion: The MCL appears to have three functional units:Superficial MCL, Deep MCL and PMC. We believe that this description allows a logical approach to understanding the biomechanics and surgical reconstruction of the posteromedial structures. We plan to use this anatomical study as the basis for further work to evaluate the how these functional units act.

Our objectives were to establish the envelope of passive movement and to demonstrate the kinematic behaviour of the knee during standard clinical tests before and after reconstruction of the anterior cruciate ligament (ACL). An electromagnetic device was used to measure movement of the joint during surgery.

Reconstruction of the ACL significantly reduced the overall envelope of tibial rotation (10° to 90° flexion), moved this envelope into external rotation from 0° to 20° flexion, and reduced the anterior position of the tibial plateau (5° to 30° flexion) (p < 0.05 for all). During the pivot-shift test in early flexion there was progressive anterior tibial subluxation with internal rotation. These subluxations reversed suddenly around a mean position of 36 ± 9° of flexion of the knee and consisted of an external tibial rotation of 13 ± 8° combined with a posterior tibial translation of 12 ± 8 mm. This abnormal movement was abolished after reconstruction of the ACL.

The meniscofemoral ligaments were studied in 84 fresh-frozen knees from 49 cadavers. Combined anterior and posterior approaches were used to identify the ligaments. In total, 78 specimens (93%) contained at least one meniscofemoral ligament. The anterior meniscofemoral ligament (aMFL) was present in 62 specimens (74%), and the posterior meniscofemoral ligament (pMFL) in 58 (69%). The 42 specimens (50%) in which both ligaments were present were from a significantly younger population than that with one MFL or none (p < 0.05). Several anatomical variations were identified, including oblique fibres of the posterior cruciate ligament (PCL), which were seen in 16 specimens (19%). These were termed the ‘false pMFL’.

The high incidence of MFLs and their anatomical variations should be borne in mind during arthroscopic and radiological examination of the PCL. It is important to recognise the oblique fibres of the PCL on MRI in order to avoid wrongly identifying them as either a pMFL or a tear of the lateral meniscus. The increased incidence of MFLs in younger donors suggests that they degenerate with age.

We compared the ability of three different posterior cruciate ligament (PCL) reconstructions to restore normal anteroposterior laxity to the knee from 0 to 130° of knee flexion.

Cadaver knees were tested intact, after PCL rupture or after bone-patellar tendon-bone grafting. Grafts were performed isometrically or with a single bundle representing the anatomical anterior PCL fibre bulk (aPC) or with a double bundle that added the posterior PCL fibre bulk (pPC). The grafts were tensioned to restore normal knee laxity at 60° of flexion, except for the pPC which was tensioned at 130°.

The isometric graft led to overconstraint as the knee extended resulting in high graft tension in extension and excess laxity in flexion. The aPC graft matched normal laxity from 0 to 60° of flexion but was lax from 90 to 130° of flexion. Only the double-bundled graft could restore normal knee laxity across the full range of flexion.

Repair of the rotator cuff requires secure reattachment, but large chronic defects cause osteoporosis of the greater tuberosity which may then have insufficient strength to allow proper fixation of the tendon. Recently, suture anchors have been introduced, but have not been fully evaluated.

We have investigated the strength of suture-to-anchor attachment, and the use of suture anchors in repairs of the rotator cuff either to the greater tuberosity or the lateral cortex of the humerus. The second method gave a significant increase in the strength of the repair (p = 0.014).

The repairs were loaded cyclically and failed at low loads by cutting into bone and tendon, casting doubt on the integrity of the repair in early mobilisation after surgery. Repairs with suture anchors did not perform better than those with conventional transosseous attachment.