Varus malalignment of the talar neck. Its effect on the position of the foot and on subtalar motion

Clinical accuracy of imaging techniques for talar neck malunion

OBJECTIVES

To compare the ability of plain radiographs, computed tomography (CT), and radiostereometric analysis (RSA) to detect changes in talus fracture fragment position and alignment using an in vitro model.

METHODS

Eight cadaveric tali were osteotomized at the talar neck. RSA beads were inserted into each talar fragment. The talus was anatomically reduced and stabilized with a pair of 3.5-mm cortical screws. Plain radiographs and RSA films were obtained. The fragments were then displaced and rotated to create a varus and supination deformity, and screw fixation was repeated in nonanatomic alignment. Displacement and rotation were directly measured. Plain radiographs and RSA were repeated, and CT scans were obtained. The RSA measurements were interpreted in a blinded fashion by an experienced researcher. Two independent blinded orthopedic trauma surgeons measured the displacement and rotation using plain films and CT. The results from each radiographic measurement were compared to the measured displacement and rotation using ANOVA.

RESULTS

Plain radiographs, RSA, and CT all underestimated the measured talar neck displacement and rotation. Radiographs underestimated displacement by 5.0 +/- 2.9 mm, RSA by 5.9 +/- 2.0 mm, and CT scans by 2.4 +/- 4.8 mm (P < 0.05). Rotation was also underestimated by all 3 techniques, but the differences among techniques were not statistically significant.

CONCLUSIONS

The most accurate imaging technique to measure displacement in talar neck malunion is CT scan. RSA was less useful as an imaging technique in this study.

Diagnosis and management of the painful ankle/foot part 1: clinical anatomy and pathomechanics

Distinctive anatomical features can be witnessed in the ankle/foot complex, affording specific pathological conditions. Disorders of the ankle/foot complex are multifactoral and features in both the clinical anatomy and biomechanics contribute to the development of ankle/foot pain. The superior tibiofibular, distal tibiofibular, talocrural, subtalar, and midtarsal joint systems must all participate in function of the ankle/foot complex, as each biomechanically contributes to functional movements and clinical disorders witnessed in the lower extremity. A clinician's ability to effectively evaluate, diagnose, and treat the distal lower extremity is largely reliant upon a foundational understanding of the clinical anatomy and biomechanics of this complex complex. Thus, clinicians are encouraged to consider these distinctions when examining and diagnosing disorders of the ankle/foot.

Post talus neck fracture reconstruction

Talar neck fractures are interesting fractures that require careful ORIF if the patient factors allow. The long-term sequelae of these fractures can be severe regardless of the quality of the reconstruction. Posttraumatic arthritis and avascular necrosis are devastating complications that are unfortunately common. Malunion and nonunion of talar neck fractures need to be evaluated carefully with attention to adjacent joints. A full workup is needed to fully evaluate the patient and fracture factors. If the patient has failed nonoperative treatment then reconstruction or salvage is considered. Reconstruction of ununited and malunited talar neck fractures can be successful if the patient is well selected. Corrective fusion is a viable alternative for those patients who have posttraumatic arthritis. Combined ankle replacement and subtalar fusion remains another motion-conserving procedure.

Comminuted talar neck fractures: a mechanical comparison of fixation techniques

OBJECTIVE

To compare the mechanical performance of 3 fixation techniques for comminuted talar neck fractures.

DESIGN

In vitro biomechanical study.

SETTING

Bioengineering research laboratory.

PARTICIPANTS

Thirty previously frozen human cadaveric tali were osteotomized across the talar neck. A wedge of bone 2 cm long and extending 50% of the medial to lateral and superior to inferior dimension of the talus was removed to create an unstable, comminuted fracture.

INTERVENTION

The specimens were randomized to one of 3 fixation groups. The first group was fixed with 3 anterior-to-posterior screws. The second group was fixed with 2 cannulated screws inserted from posterior to anterior. The third group was fixed with 1 screw from anterior to posterior and a medially applied blade plate. Specimens were embedded in acrylic cement and mounted on an Instron mechanical testing machine. Loading was applied in the dorsal-medial direction to failure.

MAIN OUTCOME MEASURES

For each specimen, the load-displacement curve, yield point, and 3 mm displacement point were recorded in response to controlled dorsal-medial loading to failure. Stiffness was calculated as the linear portion of the slope of the load (kN) versus displacement (mm) curve. Statistical analysis of the data was conducted using analysis of variance.

RESULTS

The mean yield point of each of the fixation techniques tested exceeded 1.4 kN. No statistically significant difference was found between the fixation methods, even when variations in age and sex were considered.

CONCLUSIONS

The mean yield point of the fixation techniques tested exceeds the theoretical stress across the talar neck during active motion. Anterior plate fixation provided equivalent stability to posterior screw fixation.

The Heidelberg foot measurement method: development, description and assessment

The aim of this study was to develop and evaluate a kinematic measurement method for the foot that could be applied clinically to measure foot function including all typical foot deformities. The ankle was modelled as two anatomically based hinge joints rotating around anatomical axes estimated by the use of projection angles. For the mid- and forefoot a descriptive approach was chosen by defining angles between anatomical landmarks or reference points derived from these landmarks. The motion of 17 markers on the lower leg and foot was measured during walking gait on 10 adult participants with no known abnormalities to determine the pattern of normal foot motion, assess reliability and provide a reference against which pathological foot behaviour could be compared. Functional angles for mid- and forefoot motions were developed to improve clinical applications of the data. The combination of anatomically and technically oriented marker placement on the foot is a reliable basis for reproducible kinematic measurements and the method was shown to be viable for clinical practice.

Comparison of plate and screw fixation and screw fixation alone in a comminuted talar neck fracture model

BACKGROUND

Talar neck fracture fixation has been studied in noncomminuted fracture models, but no large clinical series of comminuted fracture patterns have been published and no biomechanical studies have compared plate fixation with screw fixation in comminuted talar neck fractures.

METHODS

Nine matched pairs of fresh frozen talar specimens were stripped of soft tissue and mounted in a cylindrical jig. The talar neck was fractured using a dorsally directed shear force at a rate of 200 mm/min, and dorsal comminution was simulated by removing a 2-mm section of bone from the distal fracture fragment. One specimen from each pair was fixed with either two solid 4.0-mm partially threaded cancellous screws posterior-to-anterior just lateral to the posterior process of the talus or with a four-hole 2.0-mm minifragment plate contoured to the lateral surface of the talar neck and secured with 2.7-mm screws. A 2.7-mm fully threaded cortical screw was placed medially using a lag technique. The specimens were then loaded to failure with a dorsally directed force at a rate of 200 mm/min. Failure was defined as the load producing 2 mm of displacement. A Student's t-test analysis was used with significance set at p < or = 0.05.

RESULTS

Posterior-to-anterior screw fixation had a statistically significant higher load to failure than plate fixation (p < 0.05). Mean load to failure for the screw group was 120.7 +/- 68.5 N and 89.7 +/- 46.6 N for the plating group.

CONCLUSIONS

Plate fixation may offer substantial advantages in the ability to control the anatomic alignment of comminuted talar neck fractures, but it does not provide any biomechanical advantage compared with axial screw fixation. Further, the fixation strength of both methods was an order of magnitude lower than those found in previous studies of noncomminuted fractures.

Reconstruction after talar fractures

Malunited and nonunited talar fractures cause significant disability. Distinction between partial and total avascular necrosis (AVN) determines the choice of treatment. Patients who have minimal or no AVN and well-preserved joint cartilage may be amenable to corrective osteotomy through the malunited fracture or removal of the pseudoarthrosis. Secondary reconstruction with joint preservation leads to considerable functional improvement in painful talar malunions and nonunions in reliable patients. If symptomatic arthritis is present, arthrodeses and correction of deformity through the fusion or with additional osteotomies provide predictable results, although they do not restore normal foot function. Fusions should be limited to the affected joint. If the subtalar joint shows severe arthritic changes, every attempt should be made to salvage the ankle and talonavicular joints.

The surgical tibiotalar angle: a radiologic study

BACKGROUND

Many studies on cadaver specimens describe the hindfoot anatomy, but few measures have been defined and quantified on radiographs. Our aim was to determine the tibiotalar angle using the tibial tuberosity as a reference point.

METHODS

The tibiotalar angle, using the tibial tuberosity as reference point, was measured on anteroposterior views of 168 ankles. Bilateral radiographs were obtained in 75 patients.

RESULTS

The tibiotalar angle was 92.4 degrees (SD = 3.1) without significant intraindividual difference on the radiographs examined bilaterally. More varus was found in women and with increased age.

CONCLUSIONS

The tibial tuberosity is a reliable reference point for the measurement of the tibiotalar angle and is used in numerous operative procedures of the hindfoot. If the angle cannot be measured because of progressed destruction, the measurement can be obtained from the contralateral leg, as no significant intraindividual difference was found in the tibiotalar angle (p < 0.001).

Delayed surgical treatment for neglected or mal-reduced talar fractures

From 1993 to 2002, we treated nine patients for neglected or mal-reduced talar fractures. Average patient age was 39 (20-64) years and average follow-up 53 months. The time interval between injury and index operation ranged from 4 weeks to 4 years. Surgical procedures included open reduction with or without bone grafting in six cases, open reduction combined with ankle fusion in one case, talar neck osteotomy in one case, and talar neck osteotomy combined with subtalar fusion in one case. All cases had solid bone union. One patient developed avascular necrosis of the talus needing subsequent ankle arthrodesis. In six patients, adjacent hindfoot arthrosis occurred. The overall AOFAS ankle-hindfoot score was in average 77.4. We conclude that in neglected and mal-reduced talar fractures, surgical treatment can lead to a favourable outcome if the hindfoot joints are not arthritic.

Anatomical reconstruction of malunited talus fractures: a prospective study of 10 patients followed for 4 years

BACKGROUND

Malunions or nonunions after displaced talar fractures cause significant disability. Salvage procedures such as corrective arthrodesis do not restore normal foot function.

METHODS

Between 1994 and 2002, we treated 10 patients (aged 15-50 years) who had painful malunions with secondary anatomical reconstruction, at a mean of 1 year after sustaining displaced fractures of the talar body or neck. 5 patients were classified as type I (malunion and/or residual joint displacement), 2 as type II (nonunion with displacement) and 3 as type III (malunion with partial avascular necrosis, AVN). Correction was by an osteotomy through the malunited fracture or removal of the pseudarthrosis. Internal fixation was achieved with screws and additional bone grafting if necessary.

RESULTS

No wound healing problems or infections were seen. Solid union was obtained without redislocation in all cases, with no signs of development or progression of AVN. At a mean of 4 (1-8) years after reconstruction, all patients were satisfied with the result--except one patient who required ankle fusion 8 years after reconstruction. The mean AOFAS Ankle Hindfoot Score increased from 38 to 86 (p < 0.001).

INTERPRETATION

Secondary anatomical reconstruction with joint preservation leads to considerable functional improvement in painful talar malunions. Partial AVN does not preclude good to excellent functional results. The quality of the bone stock and joint cartilage (rather than the time from injury) appears to be important for the choice of treatment.

Fusion in posttraumatic foot and ankle reconstruction

Despite appropriate acute treatment, many foot and ankle injuries result in posttraumatic arthritis. Arthrodesis remains the mainstay of treatment of end-stage arthritis of the foot and ankle. An understanding of the biomechanics of the foot and ankle, particularly which joints are most responsible for optimal function of the foot, can help guide reconstructive efforts. A careful history and physical examination, appropriate radiographs, and, when necessary, differential selective anesthetic blocks help limit fusion to only those joints that are causing pain. Compression fixation, when possible, remains the treatment of choice. When bone defects are present, however, neutralization fixation may be necessary to prevent a secondary deformity that could result from impaction into a bone defect.

Fractures of the talar neck

Fractures of the talus have been described for 400 years. This article reviews the history of this injury and its treatment. It also discusses the modern results and complications involved with the injury and treatment.

Talus fractures: evaluation and treatment

Fractures of the talus are uncommon. The relative infrequency of these injuries in part accounts for the lack of useful and objective data to guide treatment. The integrity of the talus is critical to normal function of the ankle, subtalar, and transverse tarsal joints. Injuries to the head, neck, or body of the talus can interfere with normal coupled motion of these joints and result in permanent pain, loss of motion, and deformity. Outcomes vary widely and are related to the degree of initial fracture displacement. Nondisplaced fractures have a favorable outcome in most cases. Failure to recognize fracture displacement (even when minimal) can lead to undertreatment and poor outcomes. The accuracy of closed reduction of displaced talar neck fractures can be very difficult to assess. Operative treatment should, therefore, be considered for all displaced fractures. Osteonecrosis and malunion are common complications, and prompt and accurate reduction minimizes their incidence and severity. The use of titanium screws for fixation permits magnetic resonance imaging, which may allow earlier assessment of osteonecrosis; however, further investigation is necessary to determine the clinical utility of this information. Unrecognized medial talar neck comminution can lead to varus malunion and a supination deformity with decreased range of motion of the subtalar joint. Combined anteromedial and anterolateral exposure of talar neck fractures can help ensure anatomic reduction. Posttraumatic hindfoot arthrosis has been reported to occur in more than 90% of patients with displaced talus fractures. Salvage can be difficult and often necessitates extended arthrodesis procedures.