The effect of a collagen-elastin matrix on adhesion formation after flexor tendon repair in a rabbit model.

PURPOSE: The outcome of flexor tendon surgery is negatively affected by the formation of adhesions which can occur during the healing of the tendon repair. In this experimental study, we sought to prevent adhesion formation by wrapping a collagen-elastin scaffold around the repaired tendon segment. METHODS: In 28 rabbit hind legs, the flexor tendons of the third and fourth digits were cut and then repaired using a two-strand suture technique on the fourth digit and a four-strand technique on the third digit. Rabbits were randomly assigned to study and control groups. In the control group, the operation ended by closing the tendon sheath and the skin. In the study group, a collagen-elastin scaffold was wrapped around the repaired tendon segment in both digits. After 3 and 8 weeks, the tendons were harvested and processed histologically. The range of motion of the digits and the gap formation between the repaired tendon ends were measured. The formation of adhesions, infiltration of leucocytes and extracellular inflammatory response were quantified. RESULTS: At the time of tendon harvesting, all joints of the operated toes showed free range of motion. Four-strand core sutures lead to significantly less diastasis between the repaired tendon ends than two-strand core suture repairs. The collagen-elastin scaffold leads to greater gapping after 3 weeks compared to the controls treated without the matrix. Within the tendons treated with the collagen-elastin matrix, a significant boost of cellular and extracellular inflammation could be stated after 3 weeks which was reflected by a higher level of CAE positive cells and more formation of myofibroblasts in the αSMA stain in the study group. The inflammatory response subsided gradually and significantly until the late stage of the study. Both the cellular and extracellular inflammatory response was emphasized with the amount of material used for the repair. CONCLUSION: The use of a collagen-elastin matrix cannot be advised for the prevention of adhesion formation in flexor tendon surgery, because it enhances both cellular and extracellular inflammation. Four-strand core sutures lead to less gapping than two-strand core sutures, but at the same time, the cellular and extracellular inflammatory response is more pronounced.

Changes in length of the plantar aponeurosis during the stance phase of gait--an in vivo dynamic fluoroscopic study.

In locomotion, ligaments and muscles have been recognized to support the arch of the foot. However, it remains unclear to what extent the passive and active structures of the lower extremity support the longitudinal arch of the foot during walking. In this study, the mechanical function of the plantar aponeurosis (PA) is investigated by elongation measurements in vivo during the stance phase of gait, in combination with measurements of the mechanical properties of the PA in vitro. Fluoroscopy was used to measure the dynamic changes in PA length and the angular motion of the metatarsophalangeal joint of the first ray, measured during the stance phase (StPh) in 11 feet. Simultaneously, ground forces were measured. Additionally, four cadaver feet delivered topographic information relating to the PA, and three autopsy specimens of PA served to determine the in vitro mechanical properties of PA. The present study revealed a non-significant peak average PA shortening of 0.48% at about 32.5% StPh, followed by a significant average peak elongation of 3.6% at 77.5% StPh. This average peak elongation of 3.6% corresponds to a force of 292N, as estimated by mechanical testing of the autopsy PA specimens. Considering the maximum peak elongation measured in one volunteer of 4.8% at 76% StPh, a peak PA load of 488N might be expected. Hence, with an average body weight of 751N, as allocated to the 11 investigated feet, this maximum peak force would correspond to about 0.65×body weight. As far as we are aware, this is the first report on a dynamic fluoroscopic study of the PA in gait with an appreciable number of feet (11 feet). In conclusion, muscles contribute to support of the longitudinal arch of the foot and can possibly relax the PA during gait. The 'windlass effect' for support of the arch in this context is therefore questionable.

[Tarsometatarsal injuries--an often neglected entity]. / Lisfranc-Läsionen--häufig übersehen?

Tarsometatarsal dislocations or fracture dislocations represent infrequent, but severe injuries which endanger the structural and mechanical integrity of the midfoot if the diagnosis is missed initially. Delayed diagnosis may result in painful and disabling arthritis and the need for salvage reconstructive surgery. As such, the rationale of treatment should follow the principles of reconstruction of weight-bearing joint injuries. The degree of instability and dislocation will guide the decision for surgical intervention and anatomic reconstruction. As the clinical features of Lisfranc injuries are rarely conclusive an adequate radiographic examination of the foot employing three standard projections (dorso-plantar, lateral and 45 degrees oblique) usually supplemented by CT scans and/or MRI is decisive for a correct analysis of the injury components and an optimum selection of treatment options. Anatomic reduction and alignment are prerequisites for a good functional outcome. The reduction of the second metatarsal ray is the keystone and the first step of surgical reconstruction followed by the other structures involved. Since adequate stability is needed until definite healing has taken place the temporary transfixation of the corresponding tarsometatarsal joints employing small fragment positioning screws has substantial advantages compared with the traditional temporary K-wire arthrodesis.

Gait function after fracture-dislocation of the midtarsal and/or tarsometatarsal joints.

INTRODUCTION:: Fracture-dislocations of the Chopart or Lisfranc joint line represent rather rare injuries which usually result from high-energy trauma. During the last decade surgical therapy, including open reduction and internal fixation, had been accepted as the best way to achieve an optimum return to function. Repeatedly, it had been stated that anatomical reduction represented the prerequisite for satisfactory results. But nevertheless, despite benign appearances on postoperative radiographs, even disappointing clinical results may occur after this severe type of complex foot injury. In order to get more insight into foot function after Chopart and/or Lisfranc joint trauma and eventually characterize those parameters with most importance for surgical intervention and a non-disturbed gait function, a post-reconstruction study was performed in 25 patients after surgical therapy and definite healing. METHODS:: Twenty five patients were examined clinically according to a standardized protocol 1-8 years after injury and surgical reconstruction and the Maryland Foot Score (100-point rating scale) was calculated from clinical and anamnestic data. Further, standard radiography of the foot was performed. Five patients had suffered from an injury of the midtarsal joints, 11 patients had an isolated injury of the tarsometatarsal joints and 9 patients had a combined injury of both joint complexes. Surgery generally included open reduction and internal fixation employing AO small fragment screws and/or K-wires, sometimes supplemented by an external fixator. Generally, at the time of examination implant removal had been performed, again. Gait function was studied employing an EMED-SF 4 platform integrated into a walkway of 6 m length. Standard parameters were calculated in 9 specific masks employing the Novel-win software. Essentially, an intraindividual comparison with the data from the non-injured extremity was performed. Further, lateral-medial force indices were calculated using Novel-orthopaedics. RESULTS:: Intraindividual comparison of the local impulse distribution pattern correlated considerably well with the total count of the Maryland Foot Score. The mediolateral force index showed that patients with a former lesion of one of the foot columns (medial or lateral) tended to load the non-injured column, mainly. This could also be recognized in patients with apparently good or excellent gait function. The severity of radiographically visible posttraumatic arthrosis obviously did not influence gait function to a major degree, but a loss of length of one of the foot columns following a comminution injury component or a shift of the foot axis either in the horizontal or in the vertical direction demonstrated a substantial influence on gait quality. Due to the limited number of patients, an influence of technical variations of surgical reconstruction could not be demonstrated. CONCLUSION:: As a practical consequence of the presented study it may be concluded that the correct alignment of the foot axes, including a correct length proportion of the medial and lateral foot columns after an injury of the Chopart and/or Lisfranc joints, should represent a major goal of therapy.