The weight bearing axis of the limb goes from the pelvis to the ground and includes the hindfoot. However, the influence of hindfoot alignment on mechanical axis deviation and overall limb alignment after total knee arthroplasty (TKA) is unknown. This study aimed to assess the change in hindfoot alignment after TKA for knee osteoarthritis, the difference in mechanical axis deviation at the knee when calculated using the ground mechanical axis as compared to the conventional mechanical axis, and the effect of hindfoot alignment on the overall postoperative limb alignment after TKA. We evaluated the pre- and postoperative hip-knee-ankle (HKA) angle, conventional mechanical axis deviation (CMAD), ground mechanical axis deviation (GMAD), and tibiocalcaneal angle (TCA) in 125 patients who underwent 165 consecutive TKAs. Overall, the change in pre- and postoperative mean TCA was not significant (p=0.48) whereas it was significant (p=0.01) in knees with =15° deformity where the hindfoot valgus decreased by approximately 25%. Preoperatively, there was no significant difference between mean CMAD and mean GMAD whereas postoperatively the difference was significant (p=0.0001). Hindfoot valgus alignment of =10° was present in 22.5% of limbs and 29% limbs had a postoperative GMAD of =10 mm in spite of the limb alignment being restored to within 3° of neutral after TKA. Despite accurate restoration of limb alignment after TKA, as a result of persistent hindfoot valgus alignment the ground mechanical axis may pass lateral to the centre of the knee joint - with potential detrimental effects on bone, ligaments and implants

Background. Traditional measurements of hindfoot alignment are based on the tibio-calcaneal angle and do not take the forefoot into account. We have developed an algorithm based on standard radiographs to calculate calcaneal offset using Ground Reaction Force (GRF). Hypothesis. The GRF algorithm measures hindfoot alignment without using the tibial axis. Materials and Methods. Thirty six patients (40 feet) were included (21 female, 15 male). Mean age was 56 (SD:17). Weight bearing orthogonal radiographs were taken. Calcaneal offsets were measured using the tibio-calcaneal angles and the GRF algorithm. The two methods were compared using the Bland-Altman method. Results. Ground Reaction Force Calcaneal Offset was in agreement with traditional measurement (p< 0.05) but individual discrepancies were found. Mean measured offsets were respectively −11.5 mm (SD:10.2) and −8 mm (SD:9.3) valgus. Mean bias between the two methods was −0.88 mm. Discussion. The GRF algorithm successfully measured hindfoot alignment, and took into consideration the influence of forefoot position. The absence of a previous gold standard and variability related to radiographic protocols are a limit. Overall, angular measurements underestimated calcaneal offset. Individual discrepancies showed that including data related to forefoot position provided a more accurate assessment. This could be of particular clinical relevance for surgical planning. Unexplained total ankle replacement failures and diffuse arthritis after ankle fusion might be reduced by using this information preoperatively. Conclusion. Ground Reaction Force could improve assessment of hindfoot alignment and provide useful information for surgical planning

Background. Occasionally, patients experience new or increased ankle pain following total knee arthroplasty (TKA). The aims of this study were to determine (1) how the correction of varus malalignment of the lower limb following TKA affected changes in alignment of the ankle and hindfoot, (2) the difference in changes in alignment of the ankle and hindfoot between patients with and without ankle osteoarthritis (OA), and (3) whether the rate of ankle pain and the clinical outcome following TKA differed between the 2 groups. Methods. We retrospectively reviewed prospectively collected data of 56 patients (99 knees) treated with TKA. Among these cases, concomitant ankle OA was found in 24 ankles. Radiographic parameters of lower-limb, ankle, and hindfoot alignment were measured preoperatively and 2 years postoperatively. In addition, ankle pain and clinical outcome 2 years after TKA were compared between patients with and without ankle OA. Results. The orientation of the ankle joint line relative to the ground improved from varus 9.4° to varus 3.4°, and the valgus compensation of the hindfoot for the varus tilt of the ankle joint showed a 2.2° decrease following TKA. Patients in the group with ankle OA showed decreased flexibility of the hindfoot resulting in less preoperative valgus compensation (p = 0.022) compared with the group without ankle OA. The postoperative hindfoot alignment was similar between the 2 groups because of the smaller amount of change in patients with ankle OA. The group with ankle OA had a higher rate of increased ankle pain (38% compared with 16%) as well as a worse Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) score (mean of 22.2 compared with 14.2) following TKA. Conclusions. A considerable proportion of patients who underwent TKA had concomitant ankle OA with reduced flexibility of the hindfoot. These patients experienced increased ankle pain following TKA and a worse clinical outcome

Simultaneous arthrodesis of the ankle and subtalar joints is an established treatment option for combined ankle and subtalar arthritis or complex hindfoot deformities. The use of a curved intra medullary nail has potential advantages in terms of stability, hindfoot alignment and avoidance of the lateral neurovascular bundle. We devised a comparative description of the results of hindfoot fusion using a curved locking nail before and after the introduction of anatomically specific modifications to the device through a retrospective review of notes and radiographs of patients undergoing simultaneous ankle and subtalar fusion by retrograde intramedullary nailing using an ACE¯ (Humeral Nail. Patients undergoing the same procedure using the Tibiotalocalcaneal [TTC] Nail System [DePuy] were recruited and studied prospectively. The outcome was assessed by a combination of notes review, clinical examination and telephone questionnaire. Between 1996 and 2004, 71 arthrodeses in 67 patients have been performed. The average follow up is 27 months [3-73] and mean age 58 years. Fifty-two arthrodeses utilised the ACE humeral nail and nineteen used the newer TTC nail. Both nailing systems are locked proximally and distally and provide a short radius laterally directed distal curve. Mean time to union is 4.3 months [3-10]. Average AOFAS hindfoot score post-operatively is 65, with a mean improvement of 40 points from the pre-operative score in the TTC nail group. Post-operative complications included deep infection, amputation and a non-union rate of 10% overall. In the humeral nail group, four symptomatic stress reactions [8%] and three fractures of the tibia [6%] occurred at the tip of the nail. No stress-riser effect has to date been seen in the TTC nail group. Prominent metalwork removal has also been significantly reduced in the TTC nail group. Our results show hindfoot fusion using a curved intramedullary nail to be an effective technique in complex cases of hindfoot arthritis and deformity. Anatomically specific alterations to the nail have resulted in a significant reduction in certain complications. Alternate proximal locking options in the TTC nail have reduced prominent metalwork and, more significantly, the incidence of stress reactions and fractures appears to have been eliminated