Background:

The Lateral Intercondylar Ridge (LIR) gained notoriety with arthroscopic trans-tibial Anterior Cruciate Ligament (ACL) reconstruction where it was mistakenly used to position the ‘over the top’ guide resulting in graft malposition.

With anatomic ACL reconstruction some surgeons use the same ridge to define the anterior margin of the ACL femoral insertion in order to guide graft placement. However there is debate about whether this ridge is a consistent and reliable anatomical structure.

The aim of our study was to identify whether the LIR is a consistent anatomical structure and to define its relationship with the femoral ACL insertion.

Introduction:

The transverse acetabular ligament (TAL) antomy is not a well explored aspect of the hip joint with limited morphological description in the reviewed literature. It is often used as an anatomical landmark for orientation of the acetabular component in total hip arthroplasty (THA). There is debate as to whether it represents an appropriate guide to cup placement in THA. Present descriptions in orthopaedic literature conside it as a single plane structure to which the surgeon can align the cup. The aim of the current study was to investigate the morphology of the TAL and it was hypothesised that the current description of it being a plane would prove insufficient.

Background:

The term ‘resident's ridge’ originated from trans-tibial ACL reconstruction where a bony ridge on the medial surface of the lateral femoral condyle was mistakenly thought to represent the posterior articular margin of the condyle. This was then mistakenly used to position the ‘over the top’ guide resulting in graft malposition.

With anatomical anteromedial ACL reconstruction some surgeons use the same ridge to define the anterior margin of the ACL femoral insertion in order to guide graft placement. However there is debate about whether this ridge is a consistent and reliable anatomical structure.

There are no anatomical studies that define the features of the ‘resident's ridge’. Therefore, our aim was to identify whether the ‘resident's ridge’ is a consistent anatomical structure in non-operated human cadaveric femoral specimens.

The purpose of this study was to provide an anatomical explanation for the presence of medial proximal tibial pain in patients with patellar mal-tracking without identifiable medial tibio-femoral compartment or proximal tibial pathology.

Using cadaveric dissection we were consistently able to identify a connection between the medial patella and the medial proximal tibia including the medial hamstrings and the posterior oblique expansion. This connection is independent of the inferior patello-tibial ligament and has not previously been described in either anatomical or orthopaedic literature. The dimensions of this medial patello-tibial connection were measured using a digital microscribe. This technique also facilitated the creation of a three dimensional virtual representation of the patello-tibial connection.

In the clinical setting, patients presenting with medial proximal tibial pain who had patellar mal-tracking as identified by clinical examination and merchant radiographs underwent MRI scanning of the knee to exclude any intraarticular or proximal tibial pathology. In those patients with patellar mal-tracking that had no evidence of proximal tibial or medial compartment pathology identified, we were able to correlate the MRI finding of oedema based at the proximal medial aspect of the tibia with the cadaveric dissection findings mentioned previously. In such cases we would recommend that treatment of the medial proximal tibial pain should focus on managing the primary pathology of patella mal-tracking.

In conclusion we present a newly identified medial patello-tibial ligamentous complex that can explain the presence of medial proximal tibial pain in patients with patellar mal-tracking and no other proximal tibial or medial compartment pathology.

Conventional computer navigation systems using bone fixation have been validated in measuring anteroposterior (AP) translation of the tibia. Recent developments in non-invasive skin-mounted systems may allow quantification of AP laxity in the out-patient setting.

We tested cadaveric lower limbs (n=12) with a commercial image free navigation system using passive trackers secured by bone screws. We then tested a non-invasive fabric-strap system. The lower limb was secured at 10° intervals from 0° to 60° knee flexion and 100N of force applied perpendicular to the tibial tuberosity using a secured dynamometer. Repeatability coefficient was calculated both to reflect precision within each system, and demonstrate agreement between the two systems at each flexion interval. An acceptable repeatability coefficient of ≤3 mm was set based on diagnostic criteria for ACL insufficiency when using other mechanical devices to measure AP tibial translation.

Precision within the individual invasive and non-invasive systems measuring AP translation of the tibia was acceptable throughout the range of flexion tested (repeatability coefficient ≤1.6 mm). Agreement between the two systems was acceptable when measuring AP laxity between full extension and 40° knee flexion (repeatability coefficient ≤2.1 mm). Beyond 40° of flexion, agreement between the systems was unacceptable (repeatability coefficient >3 mm).

These results indicate that from full knee extension to 40° flexion, non-invasive navigation-based quantification of AP tibial translation is as accurate as the standard invasive system, particularly in the clinically and functionally important range of 20° to 30° knee flexion. This could be useful in diagnosis and post-operative follow-up of ACL pathology.

The anatomy of the first metatarsophalangeal (MTP) joint and, in particular, the metatarsosesamoid articulation remains poorly understood. Its effect on sesamoid function and the pathomechanics of this joint have not been described.

Fresh frozen cadaveric specimens without evidence of forefoot deformity were dissected to assess the articulating surfaces throughout a normal range of motion. The dissections were digitally reconstructed in various positions of dorsiflexion and plantarflexion using a MicroScribe, enabling quantitative analyses in a virtual 3D environment.

In 75% of specimens, there was some degree of chondral loss within the metatarsosesamoid articulation. The metatarsal surface was more commonly affected. These changes most frequently involved the tibial metatarsosesamoid joint.

The tibial sesamoid had an average excursion of 14.2 mm in the sagittal plane when the 1st MTP joint was moved from 10 degrees of plantarflexion to 60 degrees of dorsiflexion; the average excursion of the fibular sesamoid was 8.7 mm. The sesamoids also move in a medial to lateral fashion when the joint was dorsiflexed. The excursion of the tibial sesamoid was 2.8 mm when the joint was maximally dorsiflexed while that of the fibular sesamoid was 3.2 mm.

There appears to be differential tracking of the hallucal sesamoids. The tibial sesamoid has comparatively increased longitudinal excursion whilst the fibular sesamoid has comparatively greater lateral excursion.

This greater excursion of the tibial sesamoid could explain the higher incidence of sesamoiditis in this bone. The differential excursion of the 2 metatarsosesamoid articulations is also a factor that should be considered in the design and mechanics of an effective hallux MTP joint arthroplasty.

Non-invasive assessment of lower limb mechanical alignment and assessment of knee laxity using navigation technology is now possible during knee flexion owing to recent software developments. We report a comparison of this new technology with a validated commercially available invasive navigation system.

We tested cadaveric lower limbs (n=12) with a commercial invasive navigation system against the non-invasive system. Mechanical femorotibial angle (MFTA) was measured with no stress, then with 15 Nm of varus and valgus moment. MFTA was recorded at 10° intervals from full knee extension to 90° flexion. The investigator was blinded to all MFTA measurements. Repeatability coefficient was calculated to reflect each system's level of precision, and agreement between the systems; 3° was chosen as the upper limit of precision and agreement when measuring MFTA in the clinical setting based on current literature.

Precision of the invasive system was superior and acceptable in all conditions of stress throughout flexion (repeatability coefficient <2°). Precision of the non-invasive system was acceptable from extension until 60° flexion (repeatability coefficient <3°), beyond which precision was unacceptable. Agreement between invasive and non-invasive systems was within 1.7° from extension to 50° flexion when measuring MFTA with no varus / valgus applied. When applying varus / valgus stress agreement between the systems was acceptable from full extension to 30° knee flexion (repeatability coefficient <3°). Beyond this the systems did not demonstrate sufficient agreement.

These results indicate that the non-invasive system can provide reliable quantitative data on MFTA and laxity in the range relevant to knee examination.

The exact action of the Peroneus Longus muscle on the foot is not fully understood. It is involved in a number of pathological processes like tendonitis, tenosynovitis, chronic rupture and neurological conditions. It is described as having a consistent insertion to the base of the first metatarsal, but there have also been reports of significant variations and additional slips.

Our aim was to further clarify the anatomy of the main insertion of the Peroneus Longus tendon and to describe the site and frequency of other variable insertion slips.

The course of the distal peroneus longus tendon and its variable insertion was dissected in 20 embalmed, cadaveric specimens. The surface area of the main insertion footprint was measured using an Immersion Digital Microscibe and 3D mapping software. The site and frequency of the other variable insertion slips is presented.

There was a consistent, main insertion to the infero-lateral aspect of the first metatarsal in all specimens. The surface area of this insertion was found to be proportional to the length of the foot. The insertion in males was found to be significantly larger than females. The most frequent additional slip was to the medial cuneiform. Other less frequent insertion slips were present to the lesser metatarsals.

The main footprint of the Peroneus Longus tendon is on the first metatarsal. There appears to an additional slip to the medial cuneiform frequently. Although we are unsure about the significance of these additional slips, we hope it will lead to a better understanding of the mechanism of action of this muscle and its role both in the normal and pathological foot.

The arterial supply of the talus has been extensively studied in the past but there is a paucity of information on the arterial supply to the navicular and a very limited understanding of the intra-osseous supply to the surface of either of these bones. This is despite the likely importance of this supply in relation to conditions such as osteochondral lesions of the dome of the talus, and avascular necrosis and stress fracture of the navicular.

Using cadaveric limbs, dissection of the source vessels was performed followed by arterial injection of latex. The talus and navicular were then removed en bloc, preserving the integrity of the injected arterial vasculature. The specimens were then processed using a new, accelerated diaphanisation technique. This rendered the tissue transparent, allowing the injected vessels to be visualised and then mapped onto a 3D virtual reconstruction of the bone. The vasculature to the subchondral surfaces of the talus and navicular, and the source vessel entry points that provide arterial supply into the navicular were identified.

This study gives quantifiable evidence of the areas of consistently poor blood supply which may help explain the clinical pattern of talar and navicular pathology. It also provides as yet unpublished information on the arterial supply of the human navicular bone.

The extended lateral approach offers a safe surgical approach in the fixation of calcaneal fractures. Lateral plating of the calcaneum could put structures on the medial side at risk. The aim was to identify structures at risk on the medial side of the calcaneum from wires, drills or screws passed from lateral to medial.

Ten embalmed cadaveric feet were dissected. A standard extended lateral approach was performed. The DePuy perimeter plate was first applied and 2mm K-wires were drilled through each of the holes. The medial side was now examined to determine the structures at risk through each hole. The process was repeated with the Stryker plate. The calcaneum was divided into 6 zones, by two vertical lines, from the margins of the posterior facet and a transverse line along the axis of the bone through the highest point of the peroneal tubercle.

The DePuy and the Stryker plates have 12 screw positions, 5 of which are common. With both systems, screw positions in zone 1 risk injury to the medial plantar nerve and zone 3 the lateral plantar nerve. A screw through zone 2 compromises the medial plantar in both. Screws through zone 4 risk the lateral plantar nerve with the DePuy plate. Screws through zone 5 of the DePuy plate risk the medial calcaneal nerve. Zone 5 of the Stryker plate and Zone 6 of both are safe.

There is significant risk to medial structures from laterally placed wires, drills or screws. Subtalar screws have the highest risk and have to be carefully measured and placed. The Stryker plating system is relatively safer than the DePuy perimeter plate with three safe zones out of six.

Talar neck fractures are associated with high complication rates with significant associated morbidity. Adequate exposure and stable internal fixation remains challenging. We investigated the anterior extensile approach for exposure of these fractures and their fixation by screws introduced through the talo-navicular articulation. We also compared the quality and quantity of exposure of the talar neck obtained by this approach, with the classically described medial/lateral approaches.

An anterior approach to the talus between the tibialis anterior and the extensor hallucis tendons protecting both the superficial and deep peroneal nerves was performed on 5 fresh frozen cadaveric ankles . The surface area of talar neck accessible was measured using an Immersion Digital Microscribe and analysed with Rhinoceros 3D graphics package. Standard antero-medial and antero –lateral approaches were also carried out on the same ankles, and similar measurements taken. Seven talar neck fractures underwent operative fixation using the anterior approach with parallel cannulated screws inserted through the talo-navicular joint.

3D mapping demonstrated that the talar surface area visible by the anterior approach (mean 1200sqmm) is consistently superior to that visible by either the medial or lateral approaches in isolation or in combination. Medial malleolar osteotomy does not offer any additional visualisation of the talar neck. 3D reconstruction of the area visualised by the three approaches confirms that the anterior approach provides superior access to the entirety of the talar neck. 5 male and 2 female patients were reviewed. All had anatomical articular restoration, and no wound problems. None developed non union or AVN.

The anterior extensile approach offers superior visualisation of the talar neck in comparison to other approaches for anatomical articular restoration. We argue that this approach is safe, adequate and causes less vascular disruption.