It is a great challenge to perform primary TKA for patients suffering post-traumatic knee arthritis, the retained implants, residual extra-articular deformity and even the compromised femoral canal, which all hinder the use of current intramedullary guiding system to obtain accurate alignment. However, there is still no clear evidence that implants should be removed or retained in patients receiving TKA with periarticular hardware. Conversion TKA, defined as Primary TKA with periarticular implants removed simultaneously or in stage, was reported to have increased wound problems and readmission rate.[4, 6] TKA without hardware removal, including intra-operative navigation or patient specific instruments, were reported to be of value in these complicated scenarios.[5, 9, 13, 14] In this study, a simplified but facile extramedullary guiding method was proposed as alternative to perform primary TKAs in patients with arthritic knee and retained implant once computer-assisted devices were unavailable.
In the literature, computer-assisted techniques has been reported to achieve accurate alignment correction and showed similar results and complication rates compared to atraumatic osteoarthritis. However, they are not free of disadvantages or complications. For example, the prolonged surgical duration from the tracker setting and registration , the learning curve before mastering the techniques and the huge economic burden on the equipment affected the propagation and wild acceptance of computer-assisted navigation. For the later innovation, the PSBs, solved the time-consuming problem with pre-made manner. However, the time lag from image acquisition to manufacturing femur and tibia guides preparation and the additional charge (about $400–900) on the patient’s side prevent the wide adoption of this device in our daily practices.
Based on the past experiences in navigation-assisted TKAs, the authors acknowledged the strength of this computer-assisted techniques with real-time verifications.[17, 18] However, the experienced surgeons can determine and execute the adequate bone cuts to similar precision even without the aid of CAN techniques. Further, basic requirement of TKAs is to create an adequate parallel space between distal femur and proximal tibia for the implantation of prostheses. Thus, it is not hard for trained surgeons to execute the mentioned tasks with their firm and steady oscillating saws according to the prudent preoperative plan as well as the reliable verifying principles during surgery.
Compared to the literature reporting CAN-TKAs with retained implants [5, 9, 14, 19–21], our study is the first to specifically present the usefulness of free-hand techniques of proximal tibia and distal femur cuts in these complicated TKAs with retained implant. The outcomes in our series prove the mentioned ideas useful in the presence of retained hardware around the knee. Even though the initial deformity of the lower limb varies from 25ྟ varus to 10ྟ valgus, a correct alignment with a deviation less than 3 degrees was achieved in all cases after surgery. The mean ischemic time is 93.6 minutes, which was thought to be acceptable in complex knee arthroplasties. Mean hemoglobin drop was 3.2 g/dL, which was not inferior to routine primary TKA. During hospitalization, no patients required allogenic blood transfusion or prolonged inpatient stay. No patients had wound complications, periprosthetic infection and any related readmission. This may be due to the reduced surgical trauma, perioperative blood loss by not violating medullary canal as well as the limited removal of the interfering hardware. These favorable results of current study are no inferior to those using CAN or PSB in TKA with retained hardware which also report no surgical site-specific complications in their matched cohort studies.[5, 9] Manrique et al. reported significant higher mechanical failure in TKA with retained hardware compared with matched cohort. However, this condition was not observed in our patients nor the studies with retained hardware before. In the conversion TKA series, a trend of higher mechanical failure including periprosthetic fracture and loosening was also reported. We are unable to draw a conclusion that which is mechanically more fragile between TKA with retained hardware and conversion TKA. Image evaluation before operation should be done case by case to identify hindering implants that may cause suboptimal prothesis implantation. Post-operative protocols should be adjusted if stress risers are of concern.
Some inherent limitations of this study are its retrospective nature, relative short-term outcomes and the limited sample size without control group. The mentioned EM techniques of this study had been applied in our daily practice of routine primary TKAs, but this series includes only seven cases within 5 years due to the rarity of such complicated knees. Similar conditions had been reported in Hernandez’s series (1.2%). The restoration of neutral mechanical axis is believed to ensure the durability of implanted prosthesis. In the present study, the authors assessed the mechanical axis and component position using the scanogram and standard lateral radiograph. Some imaging errors were reported in the condition of flexion deformity and rotation of either femur or tibia. Further evaluation with computed tomography helps to solve the mentioned problems and to verify the actual alignment of the lower limb and the positions of prostheses. However, concerns about the additional expenditure and radiation exposure prevent the use of computed tomography in our routine image follow-ups.
We acknowledge that our method may not be suitable for the junior surgeons and not be ready for generalized practice. However, no publications report the result of TKA with retained implant using simple EM method with fewer cutting jigs. With preservation of medullary canal and retained implants, clinical benefits from less surgical trauma without compromising the operation time and expenditure were to be expected.