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.
Intramedullary pressures were better in all zones, for all cement modes, with proximal occlusion. The highest pressures were seen with Palacos-R at 4 minutes 30 seconds with proximal thumb occlusion. Stem insertion into Palacos-R at 4 minutes or 4 minutes 30 seconds, gave higher pressures than Simplex-P, with or without any form of occlusion. With Simplex-P, intramedullary pressures were higher, with Collar rather than thumb occlusion.
Poor proximal femoral pressures obtained during a cemented, primary hip replacement may lead to poor fixation of the stem to the cement and cement to bone, contributing to early aseptic loosening of the prosthesis. Occlusion of the proximal femoral area during stem insertion, especially in the region of the calcar, may help in achieving a uniform and sustained rise distally and proximally. An In-vitro analysis of femoral pressures was performed. Dental plaster was used to prepare femoral moulds in aluminium cylinders and the stem insertion phase of a cemented hip replacement was simulated with a number 3 Exeter stem, with no proximal occlusion, with thumb occlusion over the calcar and with the Exeter Horse collar. Pressure transducers were attached to the moulds. 54 experiments were performed. Of these 18 experiments were done with Palacos R cement, with the stem inserted at the recommended time of insertion and 18 with a delayed time of insertion. The last 18 experiments were performed with low viscosity Simplex P cement. Good distal pressures were obtained in all cases. However, digital occlusion helped achieve sustained, high proximal pressures as well as early, high distal pressures. The Horse collar did achieve high pressures, but only towards the end of the stem insertion phase. This was much more appreciable with low viscosity cement, where peak pressures obtained with the collar were higher than with digital occlusion. Our results show that occluding the medial cal car area is an effective way of achieving and sustaining high-pressures in the proximal and distal femur, during a hip replacement. The Exeter Horse collar is an effective means of increasing the pressure, towards the end of stem insertion, especially with low viscosity cement. Animal or cadaveric bone studies are required to show the actual penetration of cement in bone, achieved with these high pressures.