Changes in Chopart joint load following tibiotalar arthrodesis: in vitro analysis of 8 cadaver specimen in a dynamic model

Background  

In the current discussion of surgical treatment of arthroses in the ankle joint, arthrodesis is in competition with artificial joint replacement. Up until now, no valid biomechanical findings have existed on the changes in intraarticular loads following arthrodesis. One argument against tibiotalar arthrodesis is the frequently associated, long-term degeneration of the talonavicular joint, which can be attributed to changes in biomechanical stresses.     

Talonavicular arthrodesis or triple arthrodesis: Peak pressure in the adjacent joints measured in 8 cadaver specimens

Background?Talonavicular arthrodesis is a differential indication for triple arthrodesis. Differences regarding intraarticular pressure loads on the adjacent joints have not been investigated to date, but they are of clinical relevance when considering long-term joint degeneration.

Methods?We used a dynamic foot model to measure intraarticular peak pressures with electronic sensors in 8 anatomical specimens in different areas of the ankle joint and in the naviculocuneiform joint. Force was applied to extrinsic tendons via cables attached to computer- regulated hydraulic cylinders. A ground reaction force was simulated in a tilting angle- and force-controlled translation stage.

Results?We measured significantly higher peak pressures in the ankle joint after triple arthrodesis (5.7 Mpa) than after talonavicular arthrodesis (5.2 Mpa), with differences especially in the anterior section (5.2 Mpa as compared to 4.6 Mpa). Centrally, the peak pressure was similar, at 4.6?MPa and 4.5 Mpa, respectively. In the posterior area, the peak pressure after triple arthrodesis was lower (4.1?MPa as opposed to 4.4 Mpa). After triple arthrodeses, we measured higher values laterally/medially in the ankle joint (5.5?MPa/4.6 Mpa) than after talonavicular arthrodesis (5.1?MPa/4.4 Mpa). In the naviculocuneiform joint, we again saw higher peak pressures after triple arthrodesis than after talonavicular arthrodesis.

Interpretation?Our findings from this cadaver study indicate a lower and more evenly distributed peak pressure load in the ankle joint after talonavicular arthrodesis than after triple arthrodesis; thus, mechanically, a selective arthrodesis appears to be more favorable. In contrast, triple arthrodesis leads to an increase in peak pressure in the ankle joint, which may in turn lead to joint degeneration.     

Talonavicular arthrodesis or triple arthrodesis: peak pressure in the adjacent joints measured in 8 cadaver specimens

Background Talonavicular arthrodesis is a differential indication for triple arthrodesis. Differences regarding intraarticular pressure loads on the adjacent joints have not been investigated to date, but they are of clinical relevance when considering long-term joint degeneration.

Methods We used a dynamic foot model to measure intraarticular peak pressures with electronic sensors in 8 anatomical specimens in different areas of the ankle joint and in the naviculocuneiform joint. Force was applied to extrinsic tendons via cables attached to computer- regulated hydraulic cylinders. A ground reaction force was simulated in a tilting angle- and force-controlled translation stage.

Results We measured significantly higher peak pressures in the ankle joint after triple arthrodesis (5.7 Mpa) than after talonavicular arthrodesis (5.2 Mpa), with differences especially in the anterior section (5.2 Mpa as compared to 4.6 Mpa). Centrally, the peak pressure was similar, at 4.6 MPa and 4.5 Mpa, respectively. In the posterior area, the peak pressure after triple arthrodesis was lower (4.1 MPa as opposed to 4.4 Mpa). After triple arthrodeses, we measured higher values laterally/medially in the ankle joint (5.5 MPa/4.6 Mpa) than after talonavicular arthrodesis (5.1 MPa/4.4 Mpa). In the naviculocuneiform joint, we again saw higher peak pressures after triple arthrodesis than after talonavicular arthrodesis.

Interpretation Our findings from this cadaver study indicate a lower and more evenly distributed peak pressure load in the ankle joint after talonavicular arthrodesis than after triple arthrodesis; thus, mechanically, a selective arthrodesis appears to be more favorable. In contrast, triple arthrodesis leads to an increase in peak pressure in the ankle joint, which may in turn lead to joint degeneration.     

Long-term results of tibiotalar arthrodesis

One hundred and one tibiotalar arthrodeses were performed using a single surgical technique that has not been previously reported. The average follow-up was ten years (range, two to twenty-five years). The rate of pseudarthrosis was 5 per cent, four to five times less than in other recent large reports. Pseudarthrosis occurred only in patients with a sensory deficit. Secure fusion was radiographically documented in 95 per cent and the functional clinical result was good to excellent in 90 per cent. The ideal fusion position was found to be neutral or slight equinus angulation, and varus-valgus angulation equal to that of the contralateral side. More than 7 degrees of varus angulation of the heel was associated with symptomatic lateral metatarsalgia in all feet in which it occurred. Radiographic measurement documented an average 85 per cent (11-degree) increase in postoperative tarsal motion. Neither symptoms nor function correlated with the degree of tarsal hypermobility.     

Effects of a UCBL orthosis and a calcaneal osteotomy on tibiotalar contact characteristics in a cadaver flatfoot model

BACKGROUND: A flatfoot deformity alters the contact characteristics of the ankle joint, shifting the location of articulation posterolaterally, increasing pressure, and decreasing the contact area within the ankle. These changes may explain the pattern of articular degeneration and subsequent angulation observed in a long-standing adult acquired flatfoot. Corrective orthoses and surgical reconstruction have been used to realign pes planovalgus feet, but the effects of these treatments on tibiotalar contact characteristics are unknown. We hypothesized that realignment of a flatfoot with either corrective orthosis or surgical reconstruction would restore the contact characteristics of the ankle to the intact state. METHODS: The mean value of the contact area, contact pressure, peak contact pressure, and the relative locations of the global contact area and peak pressure within the ankle joint were determined from imprints created on pressure sensitive film for a series of cadaver lower limbs subjected to a weightbearing load in simulated midstance phase of gait. Each limb was loaded sequentially under four conditions: intact, flatfoot, flatfoot realigned with UCBL orthosis, and flatfoot realigned with a medial translational osteotomy of the calcaneus. RESULTS: The use of the UCBL orthosis and calcaneal osteotomy altered the contact characteristics of the ankle when compared with the flatfoot condition. Both interventions significantly decreased the mean global contact pressure from the flatfoot value, with the orthosis, demonstrating a significantly greater correction than the osteotomy. The orthosis also significantly reduced the peak contact pressure from the flatfoot value. Both interventions significantly corrected the lateral shift of the center of the peak contact pressure from the flatfoot value. The shift in the center of the global contact area approached significance when the orthosis was compared with the flatfoot. CONCLUSIONS: The changes observed in the magnitude and location of the mean and peak pressures indicate that the UCBL orthosis and calcaneal osteotomy altered hindfoot alignment to significantly influence tibiotalar contact characteristics. The results further suggest that the UCBL orthosis corrected ankle malalignment better than the calcaneal osteotomy in an adult acquired flatfoot. This study provides biomechanical data to support the clinical impression that realignment of the hindfoot corrects the pathologic tibiotalar contact characteristics associated with an adult acquired flatfoot. The results support the conclusion that the clinical management of a pes planovalgus foot with a UCBL orthosis or a medial translational osteotomy of the calcaneus may avert the onset of pantalar disease seen with late-stage posterior tibial tendon dysfunction.     

Calcaneocuboid distraction arthrodesis and first metatarsocuneiform arthrodesis for correction of acquired flatfoot deformity in a cadaver model

BACKGROUND: Lateral column lengthening has been associated with residual forefoot supination and symptomatic lateral overload in treatment of acquired flatfoot. A medial column procedure may be useful to redistribute load to the medial column. We evaluated radiographic and pressure changes in a severe flatfoot model with lateral column lengthening and investigated the effect of an added first metatarsocuneiform arthrodesis. METHODS: Ten cadaver specimens were loaded in simulated double-legged stance, and radiographic and pressure data were collected for all tested states. Calcaneocuboid arthrodesis was done with a 10-mm foam wedge. Residual forefoot varus was corrected through the first metatarsocuneiform joint. RESULTS: Differences in the mean lateral talar-first metatarsal angle, talonavicular angle, talocalcaneal angle, and calcaneal pitch were significant between the intact foot and the flatfoot. After calcaneocuboid distraction arthrodesis and tendon transfer, the lateral talar-first metatarsal angle, talonavicular angle, and calcaneal pitch were significantly different from the flatfoot. After added first metatarsocuneiform arthrodesis, the talonavicular angle was not significantly different from the intact foot. Lateral forefoot pressure increased in the flatfoot after lateral column lengthening but was not significantly different from the intact foot after first metarsocuneiform arthrodesis was added. CONCLUSIONS: Adding first metatarsocuneiform arthrodesis to calcaneocuboid distraction arthrodesis for treatment of flatfoot deformity provided improvement in radiographic and pedobarographic parameters of a severe model of stage II posterior tibial tendon dysfunction.     

Clinical outcome of tibiotalar arthrodesis utilizing the chevron technique

Tibiotalar arthrodesis remains the gold standard reconstructive procedure for the treatment of disabling ankle arthritis. The purpose of this study was to review the clinical results of tibiotalar arthrodesis utilizing the chevron fusion technique. The results of 46 consecutive patients who underwent ankle arthrodesis utilizing the chevron technique were reviewed. The etiology of the tibiotalar arthritis was posttraumatic in 29 of 46 patients. Of the remaining 17 patients, seven had osteoarthritis, five had talar osteonecrosis, two had rheumatoid arthritis, one had hemophilic arthropathy, one had gouty arthropathy, and one had unrecognized chronic osteomyelitis. Three patients had prior hindfoot arthrodeses, and two patients had bilateral ankle fusions at last follow-up. All patients were followed for a minimum of 2 years. Of the 46 patients, 41 were available for review, with an average follow-up of 7.3 years (range, 2-20 years). Twelve patients had greater than 10-year follow-up. The Mazur ankle score was calculated for all 41 patients. The average Mazur ankle score for the 41 patients available for review was 72.8, out of a maximum possible score of 90. Eighteen patients had excellent results, 11 patients had good results, five patients had fair results, and seven patients had poor results. The most common reasons for fair or poor results were symptomatic subtalar arthritis and multiple medical comorbidities. All patients with postoperative symptomatic subtalar arthritis had preoperative radiographic evidence of subtalar arthrosis. Of the 12 patients with greater than 10-year follow-up, nine had excellent or good results, and an average Mazur ankle score of 76.6. All patients with either prior hindfoot arthrodeses or bilateral ankle fusions had excellent or good results. Of the 41 arthrodeses included in the study, 38 (38/41, 93%) went on to clinical and radiographic union. The chevron technique provides a predictable method to obtain fusion of the tibiotalar joint. Most patients can expect excellent or good results. In the current study, 90% (37/41) of patients were satisfied with the outcome of their surgery and would undergo the same operation again under similar circumstances.     

Effect of first metatarsal shortening and dorsiflexion osteotomies on forefoot plantar pressure in a cadaver model

BACKGROUND: Metatarsalgia of the second ray is a common problem associated with disorders of the first metatarsal. It also occurs after the operative treatment of those disorders. Plantar pressure changes from alteration of the static and dynamic structure of the forefoot may be associated with this condition. This study evaluated changes in plantar forefoot pressure especially under the second metatarsal head after three operative procedures on the first ray. METHODS: Each of 12 cadaver foot specimens was cyclically loaded on the servohydraulic MTS Mini Bionix test frame (MTS Systems Corp., Eden Prairie, MN) with traction on the Achilles tendon. Plantar forefoot pressure was measured by the F-scan system (Tekscan, Inc., S. Boston, MA) with the foot intact, after a first metatarsal base dorsal closing-wedge osteotomy with 5-mm base length to simulate dorsal malunion, and after 5-mm and 10-mm metatarsal shortening procedures. Paired Student t-test analysis was used to compare data for the intact foot with data after each intervention. One form of Bonferroni's correction was done to establish a new alpha level to tighten the analysis and to compensate for multiple paired Student t-tests. The significance level was calculated to be 0.016 based on an original alpha level of 0.05. RESULTS: As compared with the intact foot, all three procedures on the first metatarsal resulted in significant decreases in plantar pressure under the first metatarsal head (p < 0.016). Plantar pressure under the second metatarsal head increased significantly as compared with the intact foot (p < 0.016) after all three procedures. Pressures under the third-fourth metatarsal heads increased significantly compared with the intact foot after the 5-mm and 10-mm shortenings (p < 0.016). Plantar pressure under the fifth metatarsal did not change significantly after any of the three procedures. CONCLUSIONS: Dorsiflexion osteotomy and shortening of the first metatarsal are associated with significant forefoot plantar pressure changes in a cadaver model.     

关节镜下病灶清除并半环槽加压外固定治疗全踝关节结核

目的探讨关节镜下踝关节结核病灶清除并半环槽加压外固定行踝关节融合术治疗全踝关节结核的临床经验。方法6例全踝关节结核患者，男4例，女2例；年龄28-44岁，平均33岁。病程8-23个月，平均13个月；均为单踝关节发病。其中1例伴踝部窦道形成患者曾在外院行切开引流术。术前均行至少3周的抗结核治疗。手术采用踝关节镜前外侧及前内侧入路进行结核病灶清除和胫距关节融合，并用半环槽外固定架固定。结果术后无一例发生皮肤感染及窦道形成等并发症。患者于术后2-7d，平均4d即可下地活动。术后6例均获得随访，随访时间6-42个月，平均21．3个月。6例患者于术后9-17周，平均12．5周达到骨性愈合，其中3例患者术后疼痛消失，其余3例有轻度疼痛及跛行，均无结核复发。结论对没有严重骨破坏的全踝关节结核采用关节镜下病灶清除，具有损伤小、恢复快、病灶清除彻底等优点。半环槽加压外固定，可早期下床活动，有利于融合愈合。     

Contact areas of the tibiotalar joint.

The contact areas between the articular surfaces of the talus and tibia are essential for understanding the mobility of the ankle joint. The purpose of our study was to reveal the contact area among the superior articular surface of the trochlea tali (target surface T) and the inferior articular surface of the tibia (query surface Q) under non-weight-bearing conditions in plantar flexion and dorsiflexion. Twenty cadaveric foot specimens were dissected and scanned by a three-dimensional (3D) laser scanner to obtain data point sets. These point sets were triangulated and a registration procedure performed to avoid any intersection of the two joint surfaces. For all points of the query surface Q, the closest distance to T was measured. In 11 of the 20 ankle joints, the contact area was larger in plantar flexion, in 5 it was nearly of equal size, and in 4 the two surfaces were found in a better congruence in dorsiflexion. The two articular surfaces can be in point or line contact and cause different motions while T is gliding on Q, so the original geometry of ligaments must be carefully reconstructed after injury or during total ankle replacement.     

Mosaicplasty of the talus: a joint contact analysis in a cadaver model.

Treating large osteochondral defects of the talar dome is a challenging problem for the foot and ankle surgeon. The purpose of this study was to determine if ankle joint surface mechanics can be restored by repairing large osteochondral defects with multiple osteochondral cylinder grafts. Pressure-sensitive film was used to measure total contact area and mean contact pressure of the ankle joint using a cadaver foot model. Specimens were sequentially tested evaluating the following conditions: 1) intact ankle, 2) with osteochondral defect, and 3) after mosaicplasty. An ovoid chondral defect measuring 8 x 12 mm for each specimen was consistently placed within the center of the contact zone. Multiple osteochondral grafts were harvested from donor tali and placed in the defect. Two graft arrays arranged in either a cluster of four 4 x 10 mm or two 6 x 10 mm plugs were inserted sequentially to fill the defect and were tested separately. Specimens were positioned in a neutral alignment on a custom load frame and axially loaded to 560 N with the pressure transducer in place. The transducers were then digitized and analyzed with an imaging software program. Data for total contact area and mean contact pressures for all conditions of each specimen were collected and statistically analyzed. Results demonstrated that the 6-mm grafts were less than optimal in fully restoring the defect in the contact zone of the talus. There was significant decrease in mean total contact area and increase in contact zone mean pressure compared to the intact condition (p < .05). Whereas, 4-mm plugs nearly restored joint contact area and pressure to normal levels. These findings suggest that focal talar dome defects can be repaired to restore normal ankle contact characteristics via the placement of small, osteochondral cylindrical grafts of talar origin.     

Correction of equinus deformity following midtarsal amputation by tibiotalar arthrodesis: a case report

Transtarsal amputation in a 49-year-old man was unacceptible because of associated equinus deformity of the ankle and callus formation on the sole of the foot. The equinus deformity and callus formation were corrected by fusion of the ankle in 10 degrees of dorsiflexion and advancement of the talus and os calcis anteriorly. The operation produces a larger weight-bearing area than Syme's amputation, does not disturb the normal weight-bearing fat pad underneath the os calcis, and preserves the length of the extremity as well as the motion in the subastragalar joint.