Introduction. The conventional bone resection technique in TKA is recognized as less accurate than computer-assisted surgery (CAS) and patient-matched instrumentation (PMI). However, these systems are not available to all surgeons performing TKAs. Furthermore, it was recently reported that PMI accuracy is not always better than that of the conventional bone resection technique. As such, most surgeons use the conventional technique for distal femur and proximal tibia resection, and efforts to improve bone resection accuracy with conventional technique are necessary. Here, we examined intraoperative X-rays after bone resection of the distal femur and proximal tibia with conventional bone resection technique. If the cutting angle was not good and the difference from preoperative planning was over 3º, we considered re-cutting the bone to correct the angle. Methods. We investigated 117 knees in this study. The cutting angle of the distal femur was preoperatively determined by whole-length femoral X-ray. The conventional technique with an intramedullary guide system was used for distal femoral perpendicular resection to the mechanical axis. Proximal tibial cutting was performed perpendicular to the tibial shaft with an extramedullary guide system. The cutting angles of the distal femur and proximal tibia were estimated by intraoperative X-ray with the lower limb in extension position. When the cutting angle was over 3º different from the preoperatively planned angle, re-cutting of distal femur or proximal tibia was considered. Results. On the intraoperative X-ray, the average femoral cutting angle difference from preoperative planning was 0.1º (SD: 2.6º) and the average tibial cutting angle was 1.1º varus (SD: 1.8º). Over 3º and 5º outlier cases were observed in 15 knees and 5 knees on the femoral side and in 15 knees and 3 knees on the tibial side respectively. Cutting angle correction was performed in 18 knees on the distal femur and 17 knees on the proximal tibia. On the postoperative X-ray, over 3º and 5º outliers were observed in 16 knees and only 1 knee on the femoral side and in 11 knees and no cases on the tibial side respectively. Cases with outliers over 3º were not different between intra- and postoperative estimation; however, the number of over 5º outliers was decreased from 8 knees (6.8%) to 1 knee (0.9%) including both the femoral and tibial sides (p < 0.05, Chi-square test). Discussion. Precise bone cutting technique is important for TKA; however, the bone resection accuracy of the conventional technique is far from satisfactory. CAS, PMI, and portable navigation have been developed for precise bone resection in TKA. However, these new technologies involve additional cost and have not been clearly shown to improve accuracy. Most surgeons currently use the conventional technique, and we think it is possible to improve bone resection accuracy with the conventional technique in TKA. Our method is simple and requires just one intraoperative X-ray. This is cost-effective and can be performed by most surgeons. Our results indicate that a single intraoperative X-ray can reduce the number of excessive bone resection angle outliers in TKA

Objective. In a cruciate retaining total knee arthroplasty (CR-TKA) for patients with flexion contracture, to ensure that an extension gap is of sufficient size to install an implant, the amount of distal femur bone resection needed is frequently larger in a patient with knee flexion contracture than in one without contracture. In this study, we compared the distal femur bone resection amount, the component-secured extension gap margin value, and the range of motion at 6 months after surgery between patients with knee flexion contracture and those without knee flexion contracture. Method. We examined 51 joints including 27 joints in patients with preoperative extension limitation of less than 5 degrees (the F0 group) and 24 joints in patients with limitation of 15 degrees or larger (up to 33 degrees; the FC group) who underwent CR-TKA with LCS RP (DePuy Synthes) between May 2013 and April 2014. In case with an extension gap 3 mm or smaller than the flexion gap after initial bone resection, we released posterior capsule adequately, trying to minimize the distal femur additional bone resection amount as possible. With installation of a femoral trial, the component gaps were measured using spacer blocks. The measured parameters included the intraoperative bone resection length, gap difference (FG − EG, i.e., difference between the flexion gap [FG] and extension gap [EG]), and range of motion 6 months after surgery. Results. No inter-group difference was found in the length of the distal femur bone initially resected in the medial side of distal femur(F0: 6.7 ± 1.3 mm, FC: 6.1 ± 1.4 mm) and total length of bone resection (= first + additional resection) in the lateral proximal tibia (F0: 10.3 ± 1.9 mm, FC: 10.4 ± 2.1 mm). The length of the additional distal femur bone resected was 0.9 ± 1.3 mm in the F0 and 1.5 ± 1.2 mm in the FC (P = 0.06; Mann-Whitney U). The FG-EG (F0: 0.7 ± 0.9 mm, FC: 0.6 ± 0.8 mm) showed no remarkable inter-group difference. The mean range of motion was changed from −2.3° to −0.6° at extension and from 130.4° to 128.7° at flexion in the F0 and from −19.8° to −2.7° at extension and from 113.7° to 122.3° at flexion in the FC. Conclusions. The amount of distal femur bone resected should not be simply increased because this may elevate the joint line, narrow the flexion range, and cause the joint instability in mid-flexion. The results of this study show that, in CR-TKA for patients with flexion contracture up to 30°, the length of distal femoral bone resection of approximately 1 mm larger than that in patients without contracture may ensure an extension gap of necessary and sufficient length to install an implant

To compare the volume of acetabular bone resection after primary hip arthroplasty with different cup designs and technique of implantation using a computer model. The factors influencing acetabular bone resection during acetabular cup implantation in THA or hip resurfacing (SRA) include the design of the component and technique of implantation. The impact of these variables on bone resection was simulated with a computer model. A 3-D pelvis was reconstructed from CT scan images. The bony acetabulum circumference was 52.5mm. Implantation of pressfit acetabular component sustaining angles of 165°, 170° and 180° with different wall thicknesses (3.5, 4.0, 5.0mm) at various depths was simulated. Bone loss of 2742mm3 was calculated for the 165°, 4mm thick, 54mm cup, and deepening of reaming by 1 and 2mm would result in bone loss of 3780mm3 (+38%) and 5076mm3 (+85%), respectively. When oversizing to a 56mm 165° component, 4998mm3 (+82%) of bone was removed. For a 54mm, 5 mm thick component sustaining an angle of 180°, the bone loss would reach 12 410mm3 (+450%). Acetabular component design has a significant influence on the amount of acetabular bone resection. The surgical technique (avoiding over deepening and oversised components) should minimise bone loss. This knowledge is of particular importance in hip resurfacing since the acetabular component size depends on the selected femoral component size. The knowledge is is also important in THA to minimise bone loss at primary implantation

Aims. Sagittal plane imbalance (SPI), or asymmetry between extension and flexion gaps, is an important issue in total knee arthroplasty (TKA). The purpose of this study was to compare SPI between kinematic alignment (KA), mechanical alignment (MA), and functional alignment (FA) strategies. Methods. In 137 robotic-assisted TKAs, extension and flexion stressed gap laxities and bone resections were measured. The primary outcome was the proportion and magnitude of medial and lateral SPI (gap differential > 2.0 mm) for KA, MA, and FA. Secondary outcomes were the proportion of knees with severe (> 4.0 mm) SPI, and resection thicknesses for each technique, with KA as reference. Results. FA showed significantly lower rates of medial and lateral SPI (2.9% and 2.2%) compared to KA (45.3%; p < 0.001, and 25.5%; p < 0.001) and compared to MA (52.6%; p < 0.001 and 29.9%; p < 0.001). There was no difference in medial and lateral SPI between KA and MA (p = 0.228 and p = 0.417, respectively). FA showed significantly lower rates of severe medial and lateral SPI (0 and 0%) compared to KA (8.0%; p < 0.001 and 7.3%; p = 0.001) and compared to MA (10.2%; p < 0.001 and 4.4%; p = 0.013). There was no difference in severe medial and lateral SPI between KA and MA (p = 0.527 and p = 0.307, respectively). MA resulted in thinner resections than KA in medial extension (mean difference (MD) 1.4 mm, SD 1.9; p < 0.001), medial flexion (MD 1.5 mm, SD 1.8; p < 0.001), and lateral extension (MD 1.1 mm, SD 1.9; p < 0.001). FA resulted in thinner resections than KA in medial extension (MD 1.6 mm, SD 1.4; p < 0.001) and lateral extension (MD 2.0 mm, SD 1.6; p < 0.001), but in thicker medial flexion resections (MD 0.8 mm, SD 1.4; p < 0.001). Conclusion. Mechanical and kinematic alignment (measured resection techniques) result in high rates of SPI. Pre-resection angular and translational adjustments with functional alignment, with typically smaller distal than posterior femoral resection, address this issue. Cite this article: Bone Jt Open 2024;5(8):681–687

BACKGROUND. We conducted this study to determine if the pre-surgical patient specific instrumented planning based on Computed tomography scans can accurately predict each of the femoral and tibial resections. The technique helps in optimization of component positioning and hence overall alignment thereby reducing errors. This makes it less invasive, more efficient and cost effective. The surgical plan in combination with the cutting guides determine the resection thickness, component size, femoral rotation and femoral and tibial component alignment. Several clinical studies have shown that PSI is safe, accurate and reproducible in primary TKA. Accurate preparation of the femoral and tibial surfaces will determine alignment and component positioning and this in turn reflects on function and longevity. METHODS. The study was conducted prospectively between May 2016 and December 2017 in our institution. Patients admitted over a period of these twenty months were included in the study. Patients with primary or secondary osteoarthritis (OA) and inflammatory arthritis who were suitable to undergo patient-specific TKA were included in the study. Patients with conventional instrumented TKR and those with significant deformities requiring constrain including valgus or varus of greater than 20 degrees with incompetent lateral or medial collateral ligaments were excluded from the study along with revisions of partial knee to TKA using PSI blocks. Prophecy® Preoperative Navigation 3D printed Guides were used for the Evolution Medial Pivot knee replacement system (. Microport Orthopaedics (Arlington, TN 38002, USA)). in all cases. The operating surgeon measured all the resections made (4 femoral and 2 tibial) using vernier calipers intraoperatively. These measurements were then compared with the preoperative CT predicted bone resection surgical planning. The senior author (IN) also designed markings on the tibial cutting blocks to improve accurate placement on the tibia and further markings on the femoral cutting blocks to ensure accurate positioning and rotational alignment improving accuracy of the cuts and femoral rotation. Further markings by senior surgeon (IN) on the pre-operative plans included tibial rotational plans in relation to the tibial tubercle. RESULTS. A total of 3618 readings were calculated from 201 knees (105 right and 96 left). There were 112 females and 76 males, and the average age was 67.72 years (44 to 90 years) and average BMI 32.3 (25.1 to 42.3). The surgical time ranged from 46 to 102 minutes with a mean operating time of 62 minutes. All Femoral and Tibial blocks sat accurately on the bony surfaces before being pinned. 94% of all collected resection readings were below the error margin of ≤1.5 mm of which 90% showed resection error of ≤1mm. Mean error of different resections were ≤0.60 mm (P ≤ 0.0001). In 24% of measurements there were no errors or deviations from the templated resection (0.0 mm). CONCLUSION. The 3D printed cutting blocks with slots for jigs accurately predict bone resections in PSI total knee arthroplasty which would directly affect component positioning and hence longevity and function

Introduction. Although, the total knee arthroplasty (TKA) procedure is performed to make the same extension gap (EG) and flexion gap (FG) of the knee, it is not clear how the gaps can be created equally. According to earlier reports, the gaps after bone resection (bone gaps) differ from the gaps after the trial component of the femur is set (component gaps), because of the thickness of the posterior condyle of the femoral component and the tension of the posterior capsule. The surgeon can only check the component gaps after completing the bone resection and setting the trial component and it difficult to adjust the gaps even when the acquired component gaps are inadequate. To resolve this problem, we developed a “pre-cut trial component” for use in a pre-cut technique for the femoral posterior condyle (Fig. 1). This specially made trial component allows us to check the component gaps before the final bone resection of the femur. Materials and methods. The pre-cut trial component is composed of an 8-mm-thick usual distal part and a 4-mm-thick posterior part of the femoral component, and lacks an anterior part of the femoral component. With this pre-cut trail component, 152 knees were investigated. The EG was made by standard resection of distal femur and proximal tibia. The FG was made by a 4 mm pre-cut from the posterior condylar line of the femoral posterior condyle (Fig. 2). The rotation of the pre-cut line is initially decided by anatomical landmarks. Once all of the osteophytes are removed and the bone gaps are checked, the pre-cut trial component is attached to the femur and the component gaps are estimated with the patella reduction (Fig. 3). In our experiments, these gaps were the same as the component gaps after the usual trial component was set via the measured resection technique. Finally, the femur is completely resected according to the measurements of the component gaps with the pre-cut trial component. Results. The bone gaps were 18.4±2.4 (mean ± standard deviation) mm in extension and 16.5±2.7 mm in flexion. From these results, the expected component gaps were 10.8±2.7 (bone gap −8) mm in extension and 12.5±2.7 (bone gap −4) mm in flexion. After the pre-cut trial component was set, the measured component gaps were 9.4±2.8 mm in extension and 12.5±2.8 mm in flexion. The EG became 1.5±1.0 mm smaller than expected, and the change of FG was 0.2±0.5 mm. While no large decrease of EG was noted, the variation was not insubstantial (0∼5 mm). Conclusion. The difference between the bone gap and component gap is very important for an adequate EG and FG in the TKA procedure. Yet with the conventional technique, the component gap is impossible to estimate before the final bone resection. If unacceptable results are discovered after the component gaps are estimated, the gaps are difficult to correct. With the technique we present here, the component gaps can be checked before final bone resection and truly precise gap control can be attained

Distal femur resection for correction of flexion contractures in total knee arthroplasty (TKA) can lead to joint line elevation, abnormal knee kinematics and patellofemoral problems. The aim of this retrospective study was to establish the contribution of soft tissue releases and bony cuts in the change in maximum knee extension in TKA. Data were available for 209 navigated TKAs performed by a single surgeon using a medial approach. All patients had the same cemented implant, either CR or PS, which both required a minimum thickness of 10 mm for the tibial and 9mm for the femoral component. Intra-operatively pre- and post-implant extension angles and the size of bone resection were collected using a commercial navigation system. The thickness of polyethylene insert and the extent of soft tissue release performed (no release, moderate and extensive release) were collected from the patient record. A univariate linear regression model was used to predict change in maximum extension from pre- to post-implant. The mean bone resection was 19mm (15 to 28 mm) (Figure 1).79% of polyethylene inserts were 10mm thick (10 to 16 mm). 71% of knees had no soft tissue release. The mean increase in extension was 5° (11° decrease to 23° increase) (Figure 1). The analysis showed that bone cuts (p<0.001), soft tissue release (p=0.001) and insert thickness (p=0.010) were all significant terms in the model (r. 2. adj. =0.170). This model predicted that carrying out a TKA with 19mm bone cuts, 10mm insert and no soft tissue release would give 4.2° increase in extension. It predicted that a moderate release would give a 2.8° increase in extension compared to no release, with an extensive release giving 3.9° increase over no release. For each mm increase in bone cuts the model predicted a 0.8° increase in extension and for each mm increase in insert size a decrease extension by 1.1°. Preoperative FFC contracture is a frequent condition in TKA that the surgeon has to address either by resecting more bone or by extending soft tissue release to increase the extension gap to fit the knee implant. This analysis of 209 navigated knee arthroplasty showed that both options are suitable to increase the extension gap. The modelling results show that in general to increase maximum extension by the same as an extensive soft tissue release that bone cuts would have to be increased by 4–5mm. However this model only accounted for 17% of the variation in change in extension pre- to post-implant so is poor at predicting outcomes for specific patients. The large variation in actual FFC correction indicates that this relies on factors other than bone cuts and soft tissue releases as quantified in this study

Purpose: Local resection with or without irradiation is the primary treatment modality of soft tissue sarcomas. Adequate surgical margin is required for local tumour control and avoiding local recurrence. Adjacent bone should be included into the resection plan if the tumour is in the close proximity of the bone or cortical and medullary tumour invasion was present. Reconstruction method depends on the location. Methods: 25 patient (10 female, 15 male) with soft tissue sarcomas received local wide excision including adjacent bone between 1995–2007. Histological types were 3 MPNSTM, 3MFH, 10 Synovial sarcoma, 2 liposarcoma, 4 angiosarcoma, 2 fibrosarcoma, 1 Leiomyosarcoma. Localisations were 5 glutea, 9 thigh, 5 cruris, 1 forearm, 5 foot. In 8 patients with proximal bone resection including the joint surface prosthetic reconstruction were aplied. 6 Patients with intercalary resections required allograft reconstruction with I.M nail, 2 patients required autoclaved graft, 1 patient needed tricortical iliac autograft. 8 patients in the gluteal region required iliac and sacral resections without any bony reconstruction. 25 patient received irradiation. 16 of them had neoadjuant chemotherapy also. Results: At mean 64 mo.s follow up (min11–max159). Mean age was 44, 5 (min 18–max 71). Oncologically 17 patients were NED, 1 AWD, 7 DOD (2 with local recurrence). Regarding complications 7 patients developed local recurrence, 2 patient developed infection, 2 patient had developed wound healing. 5 of 7 local recurrences were amputated. 2 of them died of the disease. 2 local recurrences could be re-resected. Delayed wound healing and infection occured in the patients received preoperative chemotherapy and irradiation. Conclusion: If a large soft tissue sarcoma is in the close proximity of an adjacent bone or had cortical or medullary invasion, adjacent bone must be included in the resection plan so that a wide margin could be achieved. Reconstruction of the created bone defect in the weight bearing bone close to a major joint should be prosthetic reconstruction. Allograft reconstruction is recommended in the foot and upper extrimity. A thorough preoperative plan with appropriate imaging should be done and local resection should be performed precisely to achieve satisfactory wide margin which influences the both local and systemic outcome

Distal femur resection for correction of flexion contractures in total knee arthroplasty (TKA) can lead to joint line elevation, abnormal knee kinematics and patellofemoral problems. The aim of this retrospective study was to establish the contribution of soft tissue releases and bony cuts in the change in maximum knee extension in TKA. Data were available for 211 TKAs performed by a single surgeon using a medial approach. Intra-operatively pre- and post-implant extension angles and the size of bone resection were collected using a commercial navigation system. The thickness of polyethylene insert and the extent of soft tissue release performed (no release, moderate and extensive release) were collected from the patient record. A linear model was used to predict change in maximum extension from pre- to post-implant. The analysis showed that bone cuts (p<0.001), soft tissue release (p=0.001) and insert thickness (p=0.010) were all significant terms in the model (r. 2. adj. =0.170). This model predicted that carrying out a TKA with 19 mm bone cuts, 10 mm insert and no soft tissue release would give 4.2° increase in extension. It predicted that a moderate release would give a further 2.8° increase in extension with an extensive release giving 3.9°. For each mm increase in bone cuts the model predicted an 0.8° increase in extension and for each mm increase in insert size a decrease extension by 1.1°. The modelling results show that in general to increase maximum extension by the same as an extensive soft tissue release that bone cuts would have to be increased by 4–5 mm. However this model only accounted for 17% of the variation in change in extension pre- to post-implant so may not be accurate at predicting outcomes for specific patients

Purpose of the study: Assessment of limb reconstruction results using vascularized fibular grafts after bony resection for malignant tumors in children. Material and methods: Thirty children (9 girls and 21 boys)underwent surgery between 1993 and 2000. Mean age was 11 years. Tumor localizations were: femur (n=17), tibia (n=6), humerus (n=5), radius (n=1) and distal ulna (n=1). Mean length of bone resection was 16 cm (range 10–26 cm). For 22 children, the adjacent epiphysis was preserved. For the eight others, fusion was also performed. Two surgical teams operated sequentially: the first team performed the tumor resection and the second (an orthopedist for the osteosynthesis and a plastician for the vascularized fibular transfer) the limb reconstruction. Radiographic and clinical assessment was completed with bone scintigraphy. The index of graft hypertrophy was determined with the De Boer and Wood method. Functional outcome was assessed with Enneking criteria. Results: Mean follow-up was 51 months (range 2 – 9 years). Early amputation was necessary for two children due to local oncological complications. One patient died of pulmonary metastasis eight months after limb reconstruction. Among the 27 other patients, primary healing was achieved in 22. In the five with primary nonunion, bone scintigraphy showed objective signs of a lack of blood supply to the graft. Secondary union was achieved with a complementary autologous bone graft in four cases. All cases of stress fracture healed with orthopedic treatment. For the 22 patients with primary union, the graft hypetrophy was 22–190% (mean 61%). For the five patients without bone vascularization on the scintigraphy, the fibular graft failed to hypertrophy. Functional outcome was satisfactory. The modified Enneking score (30 point scale) was 26 (range 19–30 points). Discussion: Limb reconstruction results are directly related to good patency of vascular anastomoses. Postoperative bone scintigraphy is useful to determine blood supply to the graft and to establish the final prognosis. In the case of vascular failure, an autologous bone graft can be proposed early to enable union. Close collaboration between the plastic surgery and the orthopedic team is the key to successful limb reconstruction with a vascularized fibular graft

Objective

In this study, we aim to compare total bone amount extracted in total knee arthroplasty in implant design and the bone amount extracted through intercondylar femoral notch cut.

Introduction. Aneurysmal bone cysts commonly found in lower limbs are locally aggressive masses that can lead to bony erosion, instability and fractures. This has major implications in the lower limbs especially in paediatric patients, with potential growth disturbance and deformity. In this case series we describe radical aneurysmal bone cyst resection and lower limb reconstruction using cable transport and syndesmosis preservation. Materials & Methods. Case 1 - A 12-year-old boy presented with a two-week history of atraumatic right ankle pain. An X-ray demonstrated a distal tibia metaphyseal cyst confirmed on biopsy as an aneurysmal bone cyst. The cyst expanded on interval X-rays from 5.5cm to 8.5cm in 9 weeks. A wide-margin en-bloc resection was performed leaving a 13.8cm tibial defect. A cable transport hexapod frame and a proximal tibial osteotomy was performed, with syndesmosis screw fixation. The transport phase lasted 11 months. While in frame, the boy sustained a distal femur fracture from a fall. The femur and the docking site were plated at the same sitting and frame removed. At one-year post-frame removal he is pain-free, with full ankle dorsiflexion but plantarflexion limited to 25 degrees. He has begun graduated return to sport. Results. Case 2 - A 12-year-old girl was referred with a three-month history of lateral left ankle swelling. X-ray demonstrated an aneurysmal bone cyst in the distal fibula metaphysis. The cyst grew from 4.2 × 2.3cm to 5.2 × 3.32cm in 2 months. A distal fibula resection (6.2cm) with syndesmosis fixation and hexapod cable transport frame were undertaken. The frame was in situ for 13 weeks and during this time she required an additional osteotomy for premature consolidation and had one pin site infection. After 13 weeks a second syndesmosis screw was placed, frame removed, and a cast applied. 3 months later she had fibular plating, BMAC and autologous iliac crest bone graft for slow union. At 3 years post-operative she has no evidence of recurrence, is pain-free and has no functional limitation. Conclusions. We describe two cases of ankle syndesmosis preservation using cable transport for juxta-articular aneurysmal bone cysts. This allows wide resection to prevent recurrence while also preserving primary ankle stability and leg length in children. Both children had a minor complication, but both had an excellent final outcome. Cable bone transport and prophylactic syndesmosis stabilization allows treatment of challenging juxta-articular aneurysmal bone cysts about the ankle. These techniques are especially useful in large bone defects

Purpose: To compare lateral closing to medial opening wedge HTO for a similar angle of correction with regard to change in proximal tibial bony anatomy and posterior cruciate ligament tibial attachment integrity following standard tibial arthroplasty resection.

Methods: Ten cadaveric lower limbs were randomized by side to receive a 12° lateral closing or 12.5mm medial opening wedge HTO. Anteroposterior, lateral and long leg AP radiographs were performed before and after each osteotomy. Pre and post osteotomy measurements of the coronal proximal tibial angle (PTA), sagittal tibial slope and anatomical femorotibial angle were completed and change in angles calculated. Prior to osteotomy, the tibial PCL attachment area was calculated. Post osteotomy, a standardized tibial arthroplasty resection was performed and the remaining percentage PCL attachment area recorded.

Results: Initial radiographs demonstrated little variation between matched pairs. Compared to the medial opening wedge group, the lateral closing wedge specimens demonstrated a statistically significant greater mean change in the PTA of 3.5° (95% C.I., 2.0 to 5.1°, p = 0.003) and an overall tendency for posterior tibial slope reduction with a mean change of −3.4 ± 4.9°. The average osteotomy angle in the medial opening wedge specimens was 11.9 ± 0.7°. Following tibial arthroplasty resection, there was a significant difference in the remaining PCL tibial attachment percentage area of 84.6 ±14.9 % for medial opening wedge and 50.8 ± 19.3 % for lateral closing wedge for a statistically significant mean difference of 33.8 % (95% C.I. 5.1 to 62.4, p = 0.031).

Conclusions: Despite similar correction angles of 12° for lateral closing and 11.9° for medial opening, the former specimens demonstrated a greater alteration in proximal tibial bony anatomy compared to the latter. In the lateral closing wedge group, the tendency to reduce posterior tibial slope and produce a greater than anticipated change in PTA had a significant effect on the integrity of the PCL’s tibial attachment following tibial arthroplasty resection.

Introduction: The use of allograft prosthetic composite (APC) of the proximal tibia offers advantages over prosthetic replacement or osteoarticular graft with a better functional outcome since the possibility of a careful soft tissue reconstruction;. Materials and Methods: From 1994 to 2002, 62 APC of the proximal tibia were performed in our department after bone tumor resection (56 malignant bone tumors, 4 cases of previously failed knee implant and 2 stage 3 benign tumors). The patients median age was 18 yrs (range: 11–77 yrs) and the mean resected length was 13.2 cm (range: 8.5–28 cm). The median follow up was 59 months (range: 13–137 months). Results: In three patients (4,8%) a recurrence was reported at 22, 33 an 40 months and amputation was performed. Infection was reported in 15 patients (24.2%): 2 early infections (healed with surgical debridment), 1 femoral stem septic loosening (treated with early revision with cemented stem); in 8 cases removal of the infected APC was required followed by implant of a new prosthetic device after cement spacer; two infections did not healed and patient underwent amputation; in two cases a good functional result was achieved removing the infected graft and covering the proximal tibia with cement and no other surgery was required. Non union of the graft was observed in 8 patients (12.9%): in 4 patients autologous bone grafting was necessary to heal the osteotomy line. In other 3 cases non union was associated with graft fracture. In one case non union was associated with tibial stem loosening and revision of the whole implant was done. Polyethylene wear was assessed in 5 patients (8%) and revision of the polyethylene components was always required. Nine patellar tendon rupture (14.5%) were assessed and repaired was performed in seven cases. The functional outcome of 42 patients with more than two years of follow up was excellent in 25 cases, good in 13, fair in 2 and poor in 2. Discussion: APC of the proximal tibia is an effective alternative to osteoarticular graft and modular prosthesis because it allows good to excellent results in most of the patients (90.4%). The major concern is infection rate (24.2%) that usually lead to amputation (80%). Non union does not usually represent a problem because it’s tendency to spontaneous or bone grafting induced healing. Aseptic loosening of the tibial or femoral stem is rare. Patellar tendon rupture rate (14.5%) is similar to modular prosthetis rate and can be lowered using a femoral component with patellar groove

Aims. Femoroacetabular impingement (FAI) patients report exacerbation of hip pain in deep flexion. However, the exact impingement location in deep flexion is unknown. The aim was to investigate impingement-free maximal flexion, impingement location, and if cam deformity causes hip impingement in flexion in FAI patients. Methods. A retrospective study involving 24 patients (37 hips) with FAI and femoral retroversion (femoral version (FV) < 5° per Murphy method) was performed. All patients were symptomatic (mean age 28 years (SD 9)) and had anterior hip/groin pain and a positive anterior impingement test. Cam- and pincer-type subgroups were analyzed. Patients were compared to an asymptomatic control group (26 hips). All patients underwent pelvic CT scans to generate personalized CT-based 3D models and validated software for patient-specific impingement simulation (equidistant method). Results. Mean impingement-free flexion of patients with mixed-type FAI (110° (SD 8°)) and patients with pincer-type FAI (112° (SD 8°)) was significantly (p < 0.001) lower compared to the control group (125° (SD 13°)). The frequency of extra-articular subspine impingement was significantly (p < 0.001) increased in patients with pincer-type FAI (57%) compared to cam-type FAI (22%) in 125° flexion. Bony impingement in maximal flexion was located anterior-inferior at femoral four and five o’clock position in patients with cam-type FAI (63% (10 of 16 hips) and 37% (6 of 10 hips)), and did not involve the cam deformity. The cam deformity did not cause impingement in maximal flexion. Conclusion. Femoral impingement in maximal flexion was located anterior-inferior distal to the cam deformity. This differs to previous studies, a finding which could be important for FAI patients in order to avoid exacerbation of hip pain in deep flexion (e.g. during squats) and for hip arthroscopy (hip-preservation surgery) for planning of bone resection. Hip impingement in flexion has implications for daily activities (e.g. putting on shoes), sports, and sex. Cite this article: Bone Joint Res 2023;12(1):22–32

Introduction and Objective. TKA have shown both excellent long-term survival rate and symptoms and knee function improvement. Despite the good results, the literature reports dissatisfaction rates around 20%. This rate of dissatisfaction could be due to the overstuff that mechanically aligned prostheses could produce during the range of motion. Either size discrepancy between bone resection and prosthetic component and constitutional mechanical tibiofemoral alignment (MTFA) alteration might increase soft tissue tension within the joint, inducing pain and functional limitation. Materials and Methods. Total knee arthroplasties performed between July 2019 and September 2020 were examined and then divided into two groups based on the presence (Group A) or absence (Group B) of patellofemoral overstuff, defined as a thickness difference of more than 2 mm between chosen component and bone resection performed, taking into account at least one of the following: femoral medial and lateral condyle, medial or lateral trochlea and patella. Based on pre and post-operative MTFA measurements, Group A was further divided into two subgroups whether the considered alignment was modified or not. Patients were assessed pre-operatively and at 6 months post-op using the Knee Society Score (KSS), Oxford Knee Score (OKS), Forgotten Joint Score (FJS), Visual Analogue Scale (VAS) and Range of Motion (ROM). Results. One hundred total knee arthroplasties were included in the present study, 69 in Group A and 31 in group B. Mean age and BMI of patients was respectively 71 and 29.2. The greatest percentage of Patellofemoral Overstuff was found at the distal lateral femoral condyle. OKS, KSS functional score, and FJS were statistically significant higher in patients without Patellofemoral Overstuff. Therefore, Group A patients with a non-modified MTFA demonstrated statistically significant better KSS, ROM and FJS. Conclusions. Patellofemoral Overstuff decrease post-operative clinical scores in patients treated with TKA. The conventional mechanically aligned positioning of TKA components might be the primary cause of prosthetic overstuffing leading to worsened clinical results. Level of evidence: III; Prospective Cohort Observational study;

INTRODUCTION. Mechanical alignment in TKA introduces significant anatomic modifications for many individuals, which may result in unequal medial-lateral or flexion-extension bone resections. The objective of this study was to calculate bone resection thicknesses and resulting gap sizes, simulating a measured resection mechanical alignment technique for TKA. METHODS. Measured resection mechanical alignment bone resections were simulated on 1000 consecutive lower limb CT-Scans from patients undergoing TKA. Bone resections were simulated to reproduce the following measured resection mechanical alignment surgical technique. The distal femoral and proximal tibial cuts were perpendicular to the mechanical axis, setting the resection depth at 8mm from the most distal femoral condyle and from the most proximal tibial plateau (Figure 1). If the resection of the contralateral side was <0mm, the resection level was increased such that the minimum resection was 0mm. An 8mm resection thickness was based on an implant size of 10mm (bone +2mm of cartilage). Femoral rotation was aligned with either the trans-epicondylar axis or with 3 degrees of external rotation to the posterior condyles. After simulation of the bone cuts, media-lateral gap difference and flexion-extension gaps difference were calculated. The gap sizes were calculated as the sum of the femoral and tibial bone resections, with a target bone resection of 16mm (+ cartilage corresponding to the implant thickness). RESULTS. For both the varus and valgus knees, the created gaps in the medial and lateral compartments were reduced in the vast majority of cases (<16mm). The insufficient lateral condyle resection distalises the lateral joint surface by a mean of 2.1mm for the varus and 4.4mm for the valgus knees. The insufficient medial tibial plateau resection proximalises the medial joint surface by 3.3mm for the varus and 1.2mm for the valgus knees. Medio-lateral gap imbalances in the extension space of more than 2mm) occurred in 25% of varus and 54% of valgus knees and significant imbalances of more than 5mm were present in up to 8% of varus and 19% of valgus knees. Higher medio-lateral gap imbalances in the flexion space were created with trans epicondylar axis versus 3 degrees to the posterior condyles (p<0.001). Using trans epicondylar axis, only 49% of varus and 18% of valgus knees had less than 3mm of imbalance in both media-lateral and flexion-extension gaps together. DISCUSSION AND CONCLUSION. A systematic use of the tested measured resection mechanical alignment technique for TKA leads to many cases with medio-lateral or flexion-extension gap asymmetries. Some medio-lateral imbalances may not be correctable surgically and may results in TKA instability. Other versions of the mechanical alignment technique or other alignment methods that better reproduce knee anatomies should be explored. For any figures or tables, please contact the authors directly

Osteosarcoma and other types of bone cancers often require bone resection, and backfill with cement. A novel silorane-based cement without PMMA's drawbacks, previously developed for dental applications, has been reformulated for orthopedic use. The aim of this study is to assess each cement's ability to elute doxorubicin, maintain its potency, and maintain suitable weight-bearing strength. The silorane-based epoxy cement was synthesized using a platinum-based Lamoreaux's catalyst. Four groups of cement were prepared. Two PMMA groups, one without any additives, one with 200 mg of doxorubicin. Two silorane groups: one without any additive, one with doxorubicin, added so that the w% of drug into both cements were equal. Pellets 6 × 12 mm were used for testing (ASTM F451). n=10. Ten pellets from each group were kept dry. All others were placed into tubes containing 2.5 mL of PBS and stored at 37 °C. Elution from doxorubicin-containing groups were collected every day for 7 days, with daily PBS changeout. Antibiotic concentrations were determined via HPLC. Compressive strength and compressive modulus of all groups were determined for unsoaked specimens, and those soaked for 7 and 14 days. MTT assays were done using an MG63 osteosarcoma cell line. Both cements were able to elute doxorubicin over 7 days in clinically-favorable quantities. For PMMA samples, the incorporation of doxorubicin was shown to significantly affect the compressive strength and modulus of the samples (p<0.01). Incorporation of doxorubicin into silorane had no significant effect on either (p>.05). MTT assays indicated that doxorubicin incorporated into the silorane cement maintained its effectiveness whereas that into PMMA did not. At the dosing used, both cements remained above the 70 MPa. Both PMMA and silorane-based cements can deliver doxorubicin. Doxorubicin, however, interacts chemically with PMMA, inhibiting polymerization and lowering the chemotherapeutic's effectiveness

In the last years, 3d printing has progressively grown and it has reached a solid role in clinical practice. The main applications brought by 3d printing in orthopedic surgery are: preoperative planning, custom-made surgical guides, custom-made im- plants, surgical simulation, and bioprinting. The replica of the patient's anatomy, starting from the elaboration of medical volumetric images (CT, MRI, etc.), allows a progressive extremization of treatment personalization that could be tailored for every single patient. In complex cases, the generation of a 3d model of the patient's anatomy allows the surgeons to better understand the case — they can almost “touch the anatomy” —, to perform a more ac- curate preoperative planning and, in some cases, to perform device positioning before going to the surgical room (i.e. joint arthroplasty). 3d printing is also commonly used to produce surgical cutting guides, these guides are positioned intraoperatively on given landmarks to guide the surgeon to perform a specific surgical act (bone osteotomy, bone resection, implant position, etc.). In total knee arthroplasty, custom-made cutting guides have been developed to help the surgeon align the femoral and tibial components to the pre-arthritic condition with- out the use of the intramedullary femoral guide. 3d printed custom-made implants represent an emerging alternative to biological reconstructions especially after oncologic resection surgery or in case of complex arthroplasty revision surgery. Custom-made implants are designed to re- place the original shape and size of the patient's bone and they allow an extreme personalization of the treatment for every single patient. Patient-specific surgical simulation is a new frontier that promises great benefits for surgical training. a solid 3d model of the patient's anatomy can faithfully reproduce the surgical complexity of the patient and it allows to generate surgical simulators with increasing difficulty to adapt the difficulties of the course with the level of the trainees performing structured training paths: from the “simple” case to the “complex” case

Aims. Dead-space management, following dead bone resection, is an important element of successful chronic osteomyelitis treatment. This study compared two different biodegradable antibiotic carriers used for dead-space management, and reviewed clinical and radiological outcomes. All cases underwent single-stage surgery and had a minimum one-year follow-up. Methods. A total of 179 patients received preformed calcium sulphate pellets containing 4% tobramycin (Group OT), and 180 patients had an injectable calcium sulphate/nanocrystalline hydroxyapatite ceramic containing gentamicin (Group CG). Outcome measures were infection recurrence, wound leakage, and subsequent fracture involving the treated segment. Bone-void filling was assessed radiologically at a minimum of six months post-surgery. Results. The median follow-up was 4.6 years (interquartile range (IQR) 3.2 to 5.4; range 1.3 to 10.5) in Group OT compared to 4.9 years (IQR 2.1 to 6.0; range 1.0 to 8.3) in Group CG. The groups had similar defect sizes following excision (both mean 10.9 cm. 3. (1 to 30)). Infection recurrence was higher in Group OT (20/179 (11.2%) vs 8/180 (4.4%), p = 0.019) than Group CG, as was early wound leakage (33/179 (18.4%) vs 18/180 (10.0%), p = 0.024) and subsequent fracture (11/179 (6.1%) vs 1.7% (3/180), p = 0.032). Group OT cases had an odds ratio 2.9-times higher of developing any one of these complications, compared to Group CG (95% confidence interval 1.74 to 4.81, p < 0.001). The mean bone-void healing in Group CG was better than in Group OT, in those with ≥ six-month radiological follow-up (73.9% vs 40.0%, p < 0.001). Conclusion. Local antibiotic carrier choice affects outcome in chronic osteomyelitis surgery. A biphasic injectable carrier with a slower dissolution time was associated with better radiological and clinical outcomes compared to a preformed calcium sulphate pellet carrier. Cite this article: Bone Joint Res 2023;12(7):412–422

Aims. Robotic-assisted total knee arthroplasty (RA-TKA) is theoretically more accurate for component positioning than TKA performed with mechanical instruments (M-TKA). Furthermore, the ability to incorporate soft-tissue laxity data into the plan prior to bone resection should reduce variability between the planned polyethylene thickness and the final implanted polyethylene. The purpose of this study was to compare accuracy to plan for component positioning and precision, as demonstrated by deviation from plan for polyethylene insert thickness in measured-resection RA-TKA versus M-TKA. Methods. A total of 220 consecutive primary TKAs between May 2016 and November 2018, performed by a single surgeon, were reviewed. Planned coronal plane component alignment and overall limb alignment were all 0° to the mechanical axis; tibial posterior slope was 2°; and polyethylene thickness was 9 mm. For RA-TKA, individual component position was adjusted to assist gap-balancing but planned coronal plane alignment for the femoral and tibial components and overall limb alignment remained 0 ± 3°; planned tibial posterior slope was 1.5°. Mean deviations from plan for each parameter were compared between groups for positioning and size and outliers were assessed. Results. In all, 103 M-TKAs and 96 RA-TKAs were included. In RA-TKA versus M-TKA, respectively: mean femoral positioning (0.9° (SD 1.2°) vs 1.7° (SD 1.1°)), mean tibial positioning (0.3° (SD 0.9°) vs 1.3° (SD 1.0°)), mean posterior tibial slope (-0.3° (SD 1.3°) vs 1.7° (SD 1.1°)), and mean mechanical axis limb alignment (1.0° (SD 1.7°) vs 2.7° (SD 1.9°)) all deviated significantly less from the plan (all p < 0.001); significantly fewer knees required a distal femoral recut (10 (10%) vs 22 (22%), p = 0.033); and deviation from planned polyethylene thickness was significantly less (1.4 mm (SD 1.6) vs 2.7 mm (SD 2.2), p < 0.001). Conclusion. RA-TKA is significantly more accurate and precise in planning both component positioning and final polyethylene insert thickness. Future studies should investigate whether this increased accuracy and precision has an impact on clinical outcomes. The greater accuracy and reproducibility of RA-TKA may be important as precise new goals for component positioning are developed and can be further individualized to the patient. Cite this article: Bone Joint J 2021;103-B(6 Supple A):74–80

Aims. Our purpose was to describe an unusual series of 21 patients with fungal osteomyelitis after an anterior cruciate ligament reconstruction (ACL-R). Methods. We present a case-series of consecutive patients treated at our institution due to a severe fungal osteomyelitis after an arthroscopic ACL-R from November 2005 to March 2015. Patients were referred to our institution from different areas of our country. We evaluated the amount of bone resection required, type of final reconstructive procedure performed, and Musculoskeletal Tumor Society (MSTS) functional score. Results. A total of 21 consecutive patients were included in the study; 19 were male with median age of 28 years (IQR 25 to 32). All ACL-R were performed with hamstrings autografts with different fixation techniques. An oncological-type debridement was needed to control persistent infection symptoms. There were no recurrences of fungal infection after median of four surgical debridements (IQR 3 to 6). Five patients underwent an extensive curettage due to the presence of large cavitary lesions and were reconstructed with hemicylindrical intercalary allografts (HIAs), preserving the epiphysis. An open surgical debridement was performed resecting the affected epiphysis in 15 patients, with a median bone loss of 11 cm (IQR 11.5 to 15.6). From these 15 cases, eight patients were reconstructed with allograft prosthesis composites (APC); six with tumour-type prosthesis (TTP) and one required a femoral TTP in combination with a tibial APC. One underwent an above-the-knee amputation. The median MSTS functional score was 20 points at a median of seven years (IQR 5 to 9) of follow-up. Conclusion. This study suggests that mucormycosis infection after an ACL-R is a serious complication. Diagnosis is usually delayed until major bone destructive lesions are present. This may originate additional massive reconstructive surgeries with severe functional limitations for the patients. Level of evidence: IV. Cite this article: Bone Joint Open 2020;2(1):3–8

Abstract. Background. Conventional TKR aims for neutral mechanical alignment which may result in a smaller lateral distal femoral condyle resection than the implant thickness. We aim to explore the mismatch between implant thickness and bone resection using 3D planning software used for Patient Specific Instrumentation (PSI) TKR. Methods. This is a retrospective anatomical study from pre-operative MRI 3D models for PSI TKR. Cartilage mapping allowed us to recreate the native anatomy, enabling us to quantify the mismatch between the distal lateral femoral condyle resection and the implant thickness. Results. We modelled 292 knees from PSI TKR performed between 2012 and 2015. There were 225 varus knees and 67 valgus knees, with mean supine hip-knee-angle of 5.6±3.1 degrees and 3.6±4.6 degrees, respectively. In varus knees, the mean cartilage loss from medial and lateral femoral condyle was 2.3±0.7mm and 1.1±0.8mm respectively; the mean overstuffing of the lateral condyle 1.9±2.2mm. In valgus knees, the mean cartilage loss from medial and lateral condyle was 1.4±0.8mm and 1.5±0.9mm respectively; the mean overstuffing of the lateral condyle was 4.1±1.9mm. Conclusions. Neutral alignment TKR often results in overstuffing of the lateral condyle. This may increase the patello-femoral pressure at the lateral facet in flexion. Anterior knee pain may be persistent even after patellar resurfacing due to tight lateral retinacular structures. An alternative method of alignment such as anatomic alignment may minimise this problem

Introduction. Studies have shown that dissatisfaction following TKA may stem from poor component placement and iatrogenic factors related to variability in surgical execution. A CT-based robotic assisted system (RA) allows surgeons to dynamically balance the joint prior to bone resection. This study aimed to determine if this system could improve TKA planning, reduce soft tissue releases, minimize bone resection, and accurately predict component size in varus knee. Method. Four hundred and seventy four cases with varus deformity undergoing primary RATKA were enrolled in this prospective, single center and surgeon study. Patient demographics and intraoperative surgical details were collected. Initial and final 3-dimensional alignment, component position, bone resection depths, use of soft tissue releases, knee balancing gaps, and component size were collected intraoperatively. WOMAC and KOOS Jr. scores were collected 6 months, and 1 year postoperatively. Descriptive statistics were applied to determine the changes in these parameters between initial and final values. Results. Native deformity ranged from 1 to 19 degrees of varus. 86% of patients in this study did not require a soft tissue release regardless of their level of coronal or sagittal deformity. Complex deformities who required a soft tissue release were corrected on average to 3 degrees varus while cases without releases were corrected to 2 degrees varus on average with the overall goal as traditional mechanical alignment. All surgeons achieved their planned sizes on the tibia and femur more than 98% of the time within one size, and 100% of the time within two sizes. Flexion and extension gaps during knee balancing were within 2mm (mean 1mm) for all knees. At latest follow-up, radiographic evidence suggested well-seated and well-fixed components. Radiographs also indicated the patella components were tracking well within the trochlear groove. No revision and re-operation were reported. Mean WOMAC total score was improved from 23.8±8.0 pre-op to 8.9±7.9 1-year post-op (p<0.01). Mean KOOS Jr. score was improved from 46.8±11.6 pre-op to 77.9±14.8 1-year post-op (p<0.01). Discussion and Conclusions. New tools may allow for enhanced execution and predictable balance for TKA, which may improve patient outcomes. In this study, preoperative planning via CT scan allowed surgeons to assess bony deformities and subtly adjust component position to reduce soft tissue trauma. While this study has several limitations, RATKA for varus knees should continue to be investigated. For any figures or tables, please contact authors directly

Introduction. Soft tissue releases are often required to correct deformity and achieve gap balance in total knee arthroplasty (TKA). However, the process of releasing soft tissues can be subjective and highly variable and is often perceived as an ‘art’ in TKA surgery. Releasing soft tissues also increases the risk of iatrogenic injury and may be detrimental to the mechanically sensitive afferent nerve fibers which participate in the regulation of knee joint stability. Measured resection TKA approaches typically rely on making bone cuts based off of generic alignment strategies and then releasing soft tissue afterwards to balance gaps. Conversely, gap-balancing techniques allow for pre-emptive adjustment of bone resections to achieve knee balance thereby potentially reducing the amount of ligament releases required. No study to our knowledge has compared the rates of soft tissue release in these two techniques, however. The objective of this study was, therefore, to compare the rates of soft tissue releases required to achieve a balanced knee in tibial-first gap-balancing versus femur-first measured-resection techniques in robotic assisted TKA, and to compare with release rates reported in the literature for conventional, measured resection TKA [1]. Methods. The number and type of soft tissue releases were documented and reviewed in 615 robotic-assisted gap-balancing and 76 robotic-assisted measured-resection TKAs as part of a multicenter study. In the robotic-assisted gap balancing group, a robotic tensioner was inserted into the knee after the tibial resection and the soft tissue envelope was characterized throughout flexion under computer-controlled tension (fig-1). Femoral bone resections were then planned using predictive ligament balance gap profiles throughout the range of motion (fig-2), and executed with a miniature robotic cutting-guide. Soft tissue releases were stratified as a function of the coronal deformity relative to the mechanical axis (varus knees: >1° varus; valgus knees: >1°). Rates of releases were compared between the two groups and to the literature data using the Fischer's exact test. Results. The overall rate of soft tissue release was significantly lower in the robotic gap-balancing group, with 31% of knees requiring one or more releases versus 50% (p=0.001) in the robotic measured resection group and 66% (p<0.001) for conventional measured resection (table-1) [1]. When comparing as a function of coronal deformity, the difference in release rates for robotic gap-balancing was significant when compared to the conventional TKA literature data (p<0.0001) for all deformity categories, but only for varus and valgus deformities for robotic measured resection with the numbers available (varus: 33% vs 50%, p=0.010; neutral 11% vs 50%, p=0.088, valgus 27% vs 53%, p=0.048). Discussion. Robotic-assisted tibial-first gap-balancing techniques allow surgeons to plan and adjust femoral resections to achieve a desired gap balance throughout motion, prior to making any femoral resections. Thus, gap balance can be achieved through adjustment of bone resections, which is accurate to 1mm/degree with robotics, rather than through manual releasing soft tissues which is subjective and less precise. These results demonstrated that the overall rate of soft tissue release is reduced when performing TKA with predictive gap-balancing and a robotic tensioning system. For any figures or tables, please contact authors directly

Aim. Adequate debridement of necrotic bone is of paramount importance for eradication of infection in chronic osteomyelitis. Currently, no tools are available to detect the exact amount of necrotic bone in order to optimize surgical resection. The aim of the present study was to evaluate the feasibility of an intraoperative illumination method (VELscope. ®. ) and the correlation between intraoperative and pathohistological findings in surgically treated chronic fracture related infection patients. Method. Ten consecutive patients with chronic fracture related infections of the lower extremity were included into this prospectively performed case series. All patients had to be treated surgically for fracture related infections requiring bony debridement. An intraoperative illumination method (VELscope®) was used to intraoperatively differentiate between viable and necrotic bone. Tissue samples from the identified viable and necrotic bone areas were histopathologically examined and compared to intraoperative findings. Results. In all included patients, the intraoperative illumination was deemed helpful to differentiate between necrotic and viable bone tissues during bony debridement. The histopathological examination of the samples showed good correlation of the intraoperative illumination findings with histopathological signs of necrosis for areas deemed dead and histopathological signs of intact bone for areas deemed vital during illumination. Conclusions. The fluorescence-assisted, intraoperative detection of necrotic and viable bone using the VELscope. ®. is an easy-to-use procedure that can help surgeons to optimize intraoperative bone resection in chronic fracture related infections by unmasking viable from necrotic bone tissue. This may help to improve resection techniques and eventually treatment outcome in patients in the future

Treatment of large bone defects represents a great challenge for orthopedic surgeons. The main causes are congenital abnormalities, traumas, osteomyelitis and bone resection due to cancer. Each surgical method for bone reconstruction leads its own burden of complications. The gold standard is considered the autologous bone graft, either of cancellous or cortical origin, but due to graft resorption and a limitation for large defect, allograft techniques have been identified. In the bone defect, these include the placement of cadaver bone or cement spacer to create the ‘Biological Chamber’ to restore bone regeneration, according to the Masquelet technique. We report eight patients, with large bone defect (for various etiologies and with an average size defect of 13.3 cm) in the lower and upper limbs, who underwent surgery at our Traumatology Department, between January 2019 and October 2020. Three patients were treated with both cortical and cancellous autologous bone grafts, while five received cortical or cement spacer allografts from donors. They underwent pre and postoperative radiographs and complete osseointegration was observed in all patients already undergoing monthly radiographic checks, with a restoration of length and range of motion. In our study, both the two stage-Masquelet and the cortical bone graft from a cadaver donor proved to be valid techniques in patients with very extensive defects to reconstruct the defect, restore the length, minimize implant left in situ and achieve complete functional recovery

Computer Assisted Surgery (CAS) and Patient Specific Instrumentation (PSI) have been reported to increase accuracy and predictability of tumour resections. The technically demanding joint-preserving surgery that retains the native joint with the better function may benefit from the new techniques. This cadaver study is to investigate the surgical accuracy of CAS and PSI in joint-preserving surgery of knee joint. CT scans of four cadavers were performed and imported into an engineering software (MIMICS, Materialise) for the 3D surgical planning of simulated, multiplanar joint-preserving resections for distal femur or proximal tibia metaphyseal bone sarcoma. The planned resections were transferred to the navigation system (OrthoMap 3D, Stryker) for navigation planning and used for the design and fabrication of the PSI. Each of the four techniques (freehand, CAS, PSI and CAS + PSI) was used in four joint-preserving resections. Location accuracy (the maximum deviation of distance between the planned and the achieved resections) and bone resection time were measured. The results were compared by using t-test (statistically significant if P< 0.05). Both the CAS+PSI and PSI techniques could reproduce the planned resections with a mean location accuracy of < 2 mm, compared to 3.6 mm for CAS assistance and 9.2 mm for the freehand technique. There was no statistical difference in location accuracy between the CAS+PSI and the PSI techniques (p=0.92) but a significant difference between the CAS technique and the CAS+PSI (p=0.042) or PSI technique (p=0.034) and the freehand technique with the other assisted techniques. The PSI technique took the lowest mean time of 4.78 ±0.97min for bone resections. This was significantly different from the CAS+PSI technique (mean 12.78 min; p < 0.001) and the CAS technique (mean 16.97 min; p = < 0.001). CAS and PSI assisted techniques help reproduce the planned multiplanar resections. The PSI technique could achieve the most accurate bone resections (within 2mm error) with the least time for bone resections. Combining CAS with PSI might not improve surgical accuracy and might increase bone resection time. However, PSI placement on the bone surface depends only on the subjective feeling of surgeons and may not apply if the extraosseous tumor component is large. Combining CAS with PSI could address the limitations

Residual tumor cells left in the bone defect after malignant bone tumor resection can result in local tumor recurrence and high mortality. Therefore, ideal bone filling materials should not only aid bone reconstruction or regeneration, but also exert local chemotherapeutic efficacy. However, common bone substitutes used in clinics are barely studied in research for local delivery of chemotherapeutic drugs. Here, we aimed to use facile manufacturing methods to render polymethylmethacrylate (PMMA) cement and ceramic granules suitable for local delivery of cisplatin to limit bone tumor recurrence. Porosity was introduced into PMMA cement by adding 1-4% carboxymethylcellulose (CMC) containing cisplatin, and chemotherapeutic activity was rendered to two types of granules via adsorption. Then, mechanical properties, porosity, morphology, drug release kinetics, ex vivo reconstructive properties of porous PMMA and in vitro anti-cancer efficacy against osteosarcoma cells were assessed. Morphologies, molecular structures, drug release profiles and in vitro cytostatic effects of two different drug-loaded granules on the proliferation of metastatic bone tumor cells were investigated. The mechanical strengths of PMMA-based cements were sufficient for tibia reconstruction at CMC contents lower than 4% (≤3%). The concentrations of released cisplatin (12.1% and 16.6% from PMMA with 3% and 4% CMC, respectively) were sufficient for killing of osteosarcoma cells, and the fraction of dead cells increased to 91.3% within 7 days. Functionalized xenogeneic granules released 29.5% of cisplatin, but synthetic CaP granules only released 1.4% of cisplatin over 28 days. The immobilized and released cisplatin retained its anti-cancer efficacy and showed dose-dependent cytostatic effects on the viability of metastatic bone tumor cells. Bone substitutes can be rendered therapeutically active for anticancer efficacy by functionalization with cisplatin. As such, our data suggest that multi-functional PMMA-based cements and cisplatin-loaded granules represent viable treatment options for filling bone defects after bone tumor resection

Background. Conventional instrumented total knee arthroplasty uses fixed angles for bony cuts followed by soft tissue releases to achieve balance. Robotic-assisted surgery allows for soft tissue balancing first then bony resection. The changes to the implant position from conventional instrumented surgery were measured and recorded. Methods. A single center, retrospective study reviewed consecutive total knee replacement surgeries over a 12 month period utilizing robotic pre-planning and balancing techniques. Changes to femoral and tibial varus/valgus and femoral rotation from traditional instrumented surgery positions were analyzed. Results. There were 145 knees which were grouped by preoperative deformity and the changes were frequent (94%), variable for any given deformity, and often unpredictable. Staged bilateral total knee arthroplasty patients also showed variability between knees. Conclusion. Robotic-assisted knee replacement technology not only has the advantage of navigation with regard to accurate implant positioning but also provides real-time, actionable data to better position the implant prior to bone resection and minimize soft tissue damage

Background. Intraoperative balancing of total knee arthroplasty (TKA) can be accomplished by either more prevalent but less predictable soft tissue releases, implant realignment through adjustments of bone resection or a combination of both. Robotic TKA allows for quantifiable precision performing bone resections for implant realignment within acceptable final component and limb alignments. Objective. To provide a direct comparison of patient reported outcomes between implant realignment and traditional ligamentous release for soft tissue balancing in TKA. Methods. IRB approved retrospective single surgeon cohort study of prospectively collected operative and clinical data of consecutive patients that underwent TKA with a single radius design utilizing kinematic sensors to assess final balance with or without robotic assistance allowing for a minimum of 12 months clinical follow up. Operative reports were reviewed to characterize the balancing strategy. In surgical cases using robotic assistance, pre-operative plan changes that altered implant placement were included in the implant realignment group. Any patient that underwent both implant realignment and soft tissue releases was analyzed separately. Kinematic sensor data was utilized to quantify ultimate balance to assure that each cohort had equivalent balance. Patient reported outcome data consisting of Knee Society- Knee Scores (KS-KS), Knee Society- Function Scores (KS-FS), and Forgotten Joint Scores (FJS) were prospectively collected during clinical follow up. Results. 182 TKA were included in the study. 3-Month clinical follow up was available for 174/182 knees (91%), 1-Year clinical follow up was available for 167/182 knees (92%) and kinematic sensor data was available for 169/182 knees (93%). Kinetic sensor data showed that on average all of the balancing subgroups achieved clinically equivalent balance. Use of robotic-arm assistance provided the tools and confidence to decrease from ligament release only in 40.8% of non-robotic cases to 3.8% in the robotic group, and the use of component realignment alone increased from 23.7% in the non-robotic cases to 48.1% in the robotic TKA group. KS-KS, KS-FS and FJS scores showed improvements in outcomes at both the 3-month and 1-year time points in the implant realignment cohort compared to the ligamentous release cohort. KS-KS, KS-FS, and FJS at 1-year were 1.6, 7.6, and 17.2 points higher respectively. While none of the comparisons reached statistical significance, KS-FS at 1 year showed a statistically and clinically significant difference (MCID 6.1–6.4) increase of 7.7 points in the implant realignment cohort compared to the ligamentous cohort. The 1-year trend can be further explained by the outperformance (MCID increase of 6.4 points) of the implant realignment robotic cohort at 1-year compared to the non-robotic ligamentous cohort. Conclusions. Directly comparing TKA patients balanced with implant realignment alone versus ligamentous release alone versus combined technique, a trend toward clinical improvement above a minimally clinical significant difference in KS-FS scores benefiting the implant realignment technique was seen at both 3-months and 1-year post-operatively. We hypothesize that the benefit of implant realignment is achieved through decreased soft tissue trauma as well as potentially greater predictability and sustainability of soft tissue balance than with soft tissue releases alone

The iASSIST system is a portable, accelerometer base with electronic navigation used for total knee arthroplasty (TKA) which guides the surgeon to align and validate bone resection during the surgical procedure. The purpose of this study was to compare the radiological outcome between accelerometer base iASSIST system and the conventional system. Method. A prospective study between two group of 36 patients (50 TKA) of primary osteoarthritis of the knee who underwent TKA using iASSIST ™ or conventional method (25 TKA in each group) from January 2018 to December 2019. A single surgeon performs all operations with the same instrumentation and same surgical approach. Pre-operative and postoperative management protocol are same for both groups. All patients had standardized scanogram (full leg radiogram) performed post operatively to determine mechanical axis of lower limb, femoral and tibial component alignment. Result. There was no significant difference between the 2 groups for Age, Gender, Body mass index, Laterality and Preoperative mechanical axis(p>0.05). There was no difference in proportion of outliers for mechanical axis (p=0.91), Coronal femoral component alignment angle (p=0.08), Coronal tibial component alignment angle (p=1.0). The mean duration of surgery, postoperative drop in Hb, number of blood transfusion didn't show significant difference between 2 groups (p>0.05). Conclusion. Our study concludes that despite being a useful guidance tool during TKA, iASSIST does not show any difference in limb alignment (mechanical axis), Tibial and femoral component alignment when compared with the conventional method

Introduction. Patient specific instrumentation (PSI) generates customized guides from an MRI- or CT-based preoperative plan for use in total knee arthroplasty (TKA). PSI software executes the preoperative planning process. Several manufacturers have developed proprietary PSI software for preoperative planning. It is possible that each proprietary software has a unique preoperative planning process, which may lead to variation in preoperative plans among manufactures and thus variation in the overall PSI technology. The purpose of this study was to determine whether different PSI software generate similar preoperative plans when applied to a single implant system and given identical MR images. Methods. In this prospective comparative study, we evaluated PSI preoperative plans generated by Materialise software and Zimmer Patient Specific Instruments software for 37 consecutive knees. All plans utilized the Zimmer Persona™ CR implant system and were approved by a single experienced surgeon blinded to the other software-generated preoperative plan. For each knee, the MRI reconstructions for both software programs were evaluated to qualitatively determine differences in bony landmark identification. The software-generated preoperative plans were assessed to determine differences in preoperative alignment, component sizes, and resection depth. PSI planned bone resection was compared to actual bone resection to assess the accuracy of intraoperative execution. Results. Materialise and Zimmer PSI software displayed differences in identification of bony landmarks in the femur and tibia. Zimmer software determined preoperative alignment to be 0.5° more varus (p=0.008) compared to Materialise software. Discordance in femoral component size prediction occurred in 37.8% of cases (p<0.001) with 11 cases differing by one size and 3 cases differing by two sizes. Tibial component size prediction was 32.4% discordant (p<0.001) with 12 cases differing by 1 size. In cases in which both software planned identical femoral component sizes, Zimmer software planned significantly more bone resection compared to Materialise in the medial posterior femur (1.5 mm, p<0.001) and lateral posterior femur (1.4 mm, p<0.001). Discussion. The present study suggests that there is notable variation in the PSI preoperative planning process of generating a preoperative plan from MR images. We found clinically significant differences with regard to bony landmark identification, component size selection, and predicted bone resection in the posterior femur between preoperative plans generated by two PSI software programs using identical MR images and a single implant system. Surgeons should be prepared to intraoperatively deviate from PSI selected size by 1 size. They should be aware that the inherent magnitude of error for PSI bone resection with regard to both planning and execution is within 2–3 mm. Users of PSI should acknowledge the variation in the preoperative planning process when using PSI software from different manufacturers. Manufacturers should continue to improve three-dimensional MRI reconstruction, bony landmark identification, preoperative alignment assessment, component size selection, and algorithms for bone resection in order to improve PSI preoperative planning process

Introduction. Robot systems have been successfully introduced to improve the accuracy and reduce severe iatrogenic soft tissue damage in knee arthroplasty. Unfortunately to perform complete a complete bone cut, the cutting tool has to slightly pass the edge of the bone. In the posterior zones were retractor protection is impossible this will lead to contact between the cutting tool and the soft tissue envelope. Therefore, complete soft tissue preservation cannot be guaranteed with the current commercial systems. Methods. This study presents an alternative robotic controlled cutting technique to perform the bone resections during TKA by milling a slot with a long slender high-speed milling tool. The system is composed by a long milling tool driven by a high-speed motor and a protector covering the end of the cutter. The protector is rigidly connected to the motor by the support structure next to the mill, which moves behind the mill in the slot created by the cutter. The protector at the end of the cutter has four functions: providing mechanical support for the mill, preventing soft tissue to come into contact with the cutter, sensing the edge of the bone to accurately follow the shape of the bone and releasing the attached soft tissue. The edge of the bone is sensed by force feedback and with the help of a probing motion the adaptive algorithm enables the protector to follow the edge of the bone closely by compensating for small segmentation and registration errors. A pilot test to evaluate the concept was performed on three fresh frozen knees. The flatness of the resection, the iatrogenic soft tissue damage, the cutting time and the efficiency of the bone contour following algorithm was measured. Results. An Rq flatness of 0.10±0.03 mm and the Rt flatness of 0.52±0.08 was obtained. The MASTI score for soft tissue damage was 34.11±1.0 resulting in two A scores and one B score. The active contour following algorithm was capable of predicting the physical location of the bone three times more accurate compared to the initial surface based registration (1.51±0.31 mm to 0.44±0.29 mm). The cutting time was 106±7 s. Discussion. The mean flatness was about three times better compared to the oscillating saw and in line with other active robots using a mill. In contrast to other orthopaedic robotic systems with a rotating cutter, this technique enables performing each resection in TKA in one movement. Therefore the new approach was significantly faster compared to other active robotic systems using a mill. Because of the active shielding of the cutter, only very little superficial soft tissue was observed. Furthermore, the adaptive bone contour approach opens the possibility for imageless active robotic knee arthroplasty. Conclusion. The promising results of this pilot study demonstrate the potential of the novel soft tissue protecting cutter by combining the accuracy of a cylindrical mill with an active soft tissue protection while reducing the cutting time

Navigation-assisted surgery has been reported to enhance resection accuracy in bone sarcoma surgery. Patient-specific instruments (PSIs) have been proposed as a simpler alternative with fewer setup facilities. We investigated the use of 3D surgical planning and PSI in realising computer planning of complex resections in bone sarcoma patients with regards to surgical accuracy, problems, and early clinical results. We retrospectively studied twelve patients with bone sarcoma treated surgically by PSIs with 3D planning. The procedure was planned using engineering software. The resection accuracy was accessed by comparing CT images of tumour specimens with the planned in seven patients. Mean age was 30.9 (9 – 64). Mean follow-up was 3.1 year (0.5 – 5.3). 31 planes of bone resections were successfully performed using the technique and were considered accurate. The mean time required for placing PSIs was 5.7 minutes (1 – 10) and performing bone osteotomies with the assistance of PSIs was 4.7 minutes (2 – 7). The mean maximum deviation error was 1.7mm (0.5 – 4.4). One PSI was broken during bone resection, and one patient needed re-resection using the same PSI. One pelvic patient died of local recurrence and lung metastases six months postoperatively. One patient developed a soft tissue local recurrence and lung metastasis at 20 months after surgery. The mean MSTS functional score was 27.9 (21 – 30). There were no complications related to 3D planning and PSIs. In selected patients, 3D surgical planning and PSIs replicate complex bone resections and reconstructions in bone sarcoma surgery. Comparative studies with conventional or navigation- assisted resections are required

Aims. The aim of this study was to assess the effect of posterior cruciate ligament (PCL) resection on flexion-extension gaps, mediolateral soft-tissue laxity, fixed flexion deformity (FFD), and limb alignment during posterior-stabilized (PS) total knee arthroplasty (TKA). Patients and Methods. This prospective study included 110 patients with symptomatic osteoarthritis of the knee undergoing primary robot-assisted PS TKA. All operations were performed by a single surgeon using a standard medial parapatellar approach. Optical motion capture technology with fixed femoral and tibial registration pins was used to assess gaps before and after PCL resection in extension and 90° knee flexion. Measurements were made after excision of the anterior cruciate ligament and prior to bone resection. There were 54 men (49.1%) and 56 women (50.9%) with a mean age of 68 years (. sd. 6.2) at the time of surgery. The mean preoperative hip-knee-ankle deformity was 4.1° varus (. sd. 3.4). Results. PCL resection increased the mean flexion gap significantly more than the extension gap in the medial (2.4 mm (. sd. 1.5) vs 1.3 mm (. sd. 1.0); p < 0.001) and lateral (3.3 mm (. sd. 1.6) vs 1.2 mm (. sd. 0.9); p < 0.01) compartments. The mean gap differences after PCL resection created significant mediolateral laxity in flexion (gap difference: 1.1 mm (. sd. 2.5); p < 0.001) but not in extension (gap difference: 0.1 mm (. sd. 2.1); p = 0.51). PCL resection significantly improved the mean FFD (6.3° (. sd. 4.4) preoperatively vs 3.1° (. sd. 1.5) postoperatively; p < 0.001). There was a strong positive correlation between the preoperative FFD and change in FFD following PCL resection (Pearson’s correlation coefficient = 0.81; p < 0.001). PCL resection did not significantly affect limb alignment (mean change in alignment: 0.2° valgus (. sd. 1.2); p = 0.60). Conclusion. PCL resection creates flexion-extension mismatch by increasing the flexion gap more than the extension gap. The increase in the lateral flexion gap is greater than the increase in the medial flexion gap, which creates mediolateral laxity in flexion. Improvements in FFD following PCL resection are dependent on the degree of deformity before PCL resection. Cite this article: Bone Joint J 2019;101-B:1230–1237

Introduction. Clinical outcomes for total knee arthroplasty (TKA) are especially sensitive to lower extremity alignment and implant positioning. 1. The use of computer-assisted orthopaedic surgery (CAOS) can improve overall TKA accuracy. 2. This study assessed the accuracy of an image-free CAOS guidance system (Exactech GPS, Blue-Ortho, Grenoble, FR) in both a synthetic leg with a normal mechanical axis and legs with abnormal mechanical axis. Materials and methods. A high-resolution 3D scanner (Comet L3D, Steinbichler, Plymouth, MI) was used to scan varus-deformed (n=12), neutral (n=12), and valgus-deformed (n=4) knee inserts (Mita M-00566, M-00598, M-00567; respectively, Medical Models, Bristol, UK) and collect pre-identified anatomical landmarks prior to using the models to simulate knee surgery. The image-free CAOS guidance system was then used to acquire the same landmarks. After adjusting the position and orientation of the cutting block to match the targets, bone resections were performed, and the knee models were re-scanned. The 3D scans made before and after the cuts were overlaid and the resection parameters calculated using the pre-identified anatomical landmark data and advanced software (UG NX, Siemens PLM, Plano, TX). Data sets obtained from the 3D scanner (see Figure 1A) were compared with data sets from the guidance system (see Figure 1B). Given the accuracy of the 3D scanner (<50μm), its measurements were used as the baseline for assessing CAOS system error. Results. Table I shows errors in bone resection thickness orientation measurement errors as well as CAOS system confidence intervals (CI) for both the tibia and femur, depending on deformity type. Regardless of knee deformity and other parameters, the mean error of the CAOS system was systematically less than 0.5 mm for bone resection measurements and 1° for joint angle measurements. The 95% CI were in the range of −1.54 to 0.67mm for bone resection measurements and −0.64° to 1.67° for joint angle measurements. No statistical differences were detected between different deformity groups in the Error Indexes for both the tibia and femur. Discussion. This study represents an extension of a previous evaluation of the same CAOS system, where only a limited number of neutral models (n=6) were investigated. The current study was performed to reassess the accuracy and precision of the CAOS system using the same methodology with a larger number of knee models (n=28) exhibiting different types of deformities affecting the mechanical axis. In conclusion, this study demonstrates a high level of in-vitro accuracy for the CAOS system, regardless of leg-alignment deformity type. The mean error of the CAOS system, characterized as the difference between the measured and checked values, was systematically less than 0.5 mm for bone resection measurements and 1° for joint angle measurements

Restoring native hip biomechanics is crucial to the success of THA. This is reflected both in terms of complications after surgery such as instability, leg length inequality, pain and limp; and in terms of patient satisfaction. The challenge that remains is that of achieving optimal implant sizing and positioning so as to restore, as closely as possible, the native hip biomechanics specific to the hip joint being replaced. This would optimise function and reduce complications, particularly, instability. (Mirza et al., 2010). Ideally, this skill should also be reproducible irrespective of the surgeon's experience, volume of surgery and learning curve. The general consensus is that the most substantial limiting factor in a THA is the surgeon's performance and as a result, human errors and unintended complications are not completely avoidable (Tarwala and Dorr, 2011). The more challenging aspects include acetabular component version, sizing and femoral component sizing, offset and position in the femoral canal. This variability has led to interest in technologies for planning THA, and technologies that help in the execution of the procedure. Advances in surgical technology have led to the development of computer navigation and robotic systems, which assist in pre-operative planning and optimise intra-operative implant positioning. The evolution of surgical technology in lower limb arthroplasty has led to the development of computer navigation and robotics, which are designed to minimise human error and improve implant positioning compared to pre-operative templating using plain radiographs. It is now possible to use pre-operative computerised tomography (image-based navigation) and/or anatomical landmarks (non-imaged-based navigation) to create three-dimensional images of each patient's unique anatomy. These reconstructions are then used to guide bone resection, implant positioning and lower limb alignment. The second-generation RIO Robotic Arm Interactive Orthopaedic system (MAKO Surgical) uses pre-operative computerised tomography to build a computer-aided design (CAD) model of the patient's hip. The surgeon can then plan and execute optimal sizing and positioning of the prostheses to achieve the required bone coverage, minimise bone resection, restore joint anatomy and restore lower limb biomechanics. The MAKO robotic software processes this information to calculate the volume of bone requiring resection and creates a three-dimensional haptic window for the RIO-robotic arm to resect. The RIO-robotic arm has tactile and audio feedback to resect bone to a high degree of accuracy and preserve as much bone stock as possible. We have used this technology in the hip to accurately reproduce the anteversion, closure and center of rotation that was planned for each hip. Whilst the precise safe target varies from patient to patient, the ability to reproduce native biomechanics, to gain fixation as planned and to get almost perfect length and offset are a great advantage. Complications such as instability and leg length inequality are thus dramatically reduced

Fixed flexion contracture is often present in association with osteoarthritis of the knee and correction is one of the key surgical goals in total knee replacement. Surgical strategies to correct flexion contracture include removal of posterior osteophytes, posterior capsular release and additional distal femoral bone resection. Traditional teaching indicates 2 mm of additional distal femoral bone resection will correct 10 degrees of flexion deformity. However some studies have questioned this figure and removing excessive distal femoral bone results in elevation of the joint line, potentially causing patella baja, alteration in collateral ligament tension through the flexion arc and mid-flexion instability. The aim of our study is to determine the relationship between distal bone resection of the femur and passive knee extension in total knee arthroplasty. A cohort of 50 patients, undergoing total knee arthroplasty, was recruited. Following complete femoral and tibial bone preparation, to simulate the effect of distal femoral bone resection, augments of 2 mm increments (2 mm, 4 mm, 6 mm, 8 mm) were placed onto the trial femoral component. The degree of flexion contracture with each augment was measured using computer navigation. The results showed a 2 mm augment produced an average of 3.37 degrees of flexion deformity. A 4 mm augment led to an average of 6.68 degrees fixed flexion, whilst a 6 mm augment produced 11.38 degrees. To correct 10 degrees flexion deformity, an additional 6 mm distal femoral bone resection is required. In conclusion, additional distal femoral bone resection may not be as an effective strategy as previously believed to correct fixed flexion deformity in total knee arthroplasty

Background. Despite the success of total knee arthroplasty (TKA) restoration of normal function is often not achieved. Soft-tissue balance is a major factor leading to poor outcomes including malalignment, instability, excessive wear, and subluxation. Mechanical ligament balancers only measure the joint space in full extension and at 90° flexion. This study uses a novel electronic ligament balancer to measure the ligament balance in normal knees and in knees after TKA to determine the impact on passive and active kinematics. Methods. Fresh-frozen cadaver legs (N = 6) were obtained. A standard cruciate-retaining TKA was performed using measured resection approach and computer navigation (Stryker Navigation, Kalamazoo, MI). Ligament balance was measured using a novel electronic balancer (Fig 1, XO1, XpandOrtho, Inc, La Jolla, CA, USA). The XO1 balancer generates controlled femorotibial distraction of up to 120N. The balancer only requires a tibial cut and can be used before or after femoral cuts, or after trial implants have been mounted. The balancer monitors the distraction gap and the medial and lateral gaps in real time, and graphically displays gap measurements over the entire range of knee flexion. Gap measurements can be monitored during soft-tissue releases without removing the balancer. Knee kinematics were measured during active knee extension (Oxford knee rig) and during passive knee extension under varus and valgus external moment of 10Nm in a passive test rig. Sequence of testing and measurement:. Ligament balance was recorded with the XO1 balancer after the tibial cut, after measured resection of the femur, and after soft-tissue release and/or bone resection to balance flexion-extension and mediolateral gaps. Passive and active kinematics were measured in the normal knee before TKA, after measured resection TKA, and after soft-tissue release and/or bone resection to balance flexion-extension and mediolateral gaps. Results & Discussion. Overall the changes in knee balance affected passive kinematics more than active kinematics. Correcting a tight extension gap by resecting 4 mm from the distal femur had a significant effect on femoral rollback and tibial rotation and increased the varus-valgus laxity of the knee (Fig 2). Sequential release of the MCL increased active femoral rollback and tibial internal rotation primarily in flexion (Fig 3). Combinations of bone resections with ligament release had an additive effect. For example, MCL release combined with 2 mm resection of bone at the distal femoral cut increased total valgus laxity by 8° during passive testing. However, even after balancing the flexion-extension gap and the mediolateral gap knee kinematics were significantly different from the normal knee before TKA. Conclusions. The XO1 electronic balancer was very sensitive to changes in bone resection and sequential soft-tissue releases. Intraoperative ligament balance had a significant effect on active and passive kinematics. However, balancing the flexion-extension gap and the mediolateral gap did not restore kinematics to that of the normal knee. Ligament balance can have a profound impact on postoperative function, and that current recommendations for balancing the knee likely have to be reconsidered

Introduction. Robot-assisted total knee arthroplasty (RA-TKA) is theoretically more accurate for component positioning than TKA performed with mechanical instruments (M-TKA). Furthermore, the ability to quantify soft tissue laxity and adjust the plan prior to bone resection should reduce variability in polyethylene thickness. This study was performed to compare accuracy to plan for component positioning and polyethylene thickness in RA-TKA versus M-TKA. Methods. 199 consecutive primary TKAs (96 C-TKA and 103 RA-TKA) performed by a single surgeon were reviewed. Full-length standing and knee radiographs were obtained pre and post-operatively. For M-TKA, measured resection technique was used. Planned coronal plane femoral and tibial component alignment, and overall limb alignment were all 0° to the mechanical axis; tibial posterior slope was 2°; and polyethylene thickness was 9mm. For RA-TKA, individual component position was adjusted to assist balance the gaps but planned coronal plane alignment for the femoral and tibial components and overall limb alignment had to remain 0+/− 3°; planned tibial posterior slope was 1.5°. Planned values and polyethylene thickness for RA-TKA were obtained from the final intra-operative plan. Mean deviations from plan for each parameter were compared between groups (ΔFemur, ΔTibia, ΔPS, and polyethylene thickness) as were distal femoral recut and tourniquet time. Results. In RA-MKA versus M-TKA: the ΔFemur (0.9 ° v. 1.7 °), ΔTibia (0.3 ° v. 1.3 °), and ΔPS (−0.3 ° v. 1.7 °) all deviated significantly less from plan (all p<0.0001); significantly fewer knees required distal femoral recut (10% vs. 23%, p=0.033); and deviation from planned polyethylene thickness was significantly less (1.4mm vs 2.7mm, p<0.0001. However, tourniquet time was longer (99 minutes v. 89 minutes, p<0.0001). Conclusion. RA-TKA is both significantly more accurate to plan for component positioning and final polyethylene thickness. The greater accuracy and reproducibility of RA-TKA may be important as precise new goals for component positioning are developed

Mechanical alignment (MA) techniques for total knee arthroplasty (TKA) may introduce significant anatomic modifications, as it is known that few patients have neutral femoral, tibial or overall lower limb mechanical axes. A total of 1000 knee CT-Scans were analyzed from a database of patients undergoing TKA. MA tibial and femoral bone resections were simulated. Femoral rotation was aligned with either the trans-epicondylar axis (TEA) or with 3° of external rotation to the posterior condyles (PC). Medial-lateral (DML) and flexion-extension (DFE) gap differences were calculated. Extension space ML imbalances (3mm) occurred in 25% of varus and 54% of valgus knees and significant imbalances (5mm) were present in up to 8% of varus and 19% of valgus knees. For the flexion space DML, higher imbalance rates were created by the TEA technique (p < 0 .001). In valgus knees, TEA resulted in a DML in flexion of 5 mm in 42%, compared to 7% for PC. In varus knees both techniques performed better. When all the differences between DML and DFE are considered together, using TEA there were 18% of valgus knees and 49% of varus knees with < 3 mm imbalances throughout, and using PC 32% of valgus knees and 64% of varus knees. Significant anatomic modifications with related ML or FE gap imbalances are created using MA for TKA. Using MA techniques, PC creates less imbalances than TEA. Some of these imbalances may not be correctable by the surgeon and may explain post-operative TKA instability. Current imaging technology could predict preoperatively these intrinsic imitations of MA. Other alignment techniques that better reproduce knee anatomies should be explored

Mechanical alignment (MA) techniques for total knee arthroplasty (TKA) introduces significant anatomic modifications and secondary ligament imbalances. A restricted kinematic alignment (rKA) protocol was proposed to minimise these issues and improve TKA clinical results. A total of 1000 knee CT-Scans were analyzed from a database of patients undergoing TKA. rKA tibial and femoral bone resections were simulated. rKA is defined by the following criteria: Independent tibial and femoral cuts within ± 5° of the bone neutral mechanical axis and, a resulting HKA within ± 3° of neutral. Medial-lateral (ΔML) and flexion-extension (ΔFE) gap differences were calculated and compared with MA results. With the MA technique, femoral rotation was aligned with either the trans-epicondylar axis (TEA) or with 3° of external rotation to the posterior condyles (PC). Extension space ML imbalances (>/=3mm) occurred in 33% of TKA with MA technique versus 8% of the knees with rKA (p /=5mm) were present in up to 11% of MA knees versus 1% rKA (p < 0 .001). Using the MA technique, for the flexion space ΔML, higher imbalance rates were created by the TEA technique (p < 0 .001). rKA again performed better than both MA techniques using TEA of 3 degrees PC techniques (p < 0 .001). When all the differences between ΔML and ΔFE are considered together: using TEA there were 40.8% of the knees with < 3 mm imbalances throughout, using PC this was 55.3% and using rKA it was 91.5% of the knees (p < 0 .001). Significantly less anatomic modifications with related ML or FE gap imbalances are created using rKA versus MA for TKA. Using rKA may help the surgeon to balance a TKA, whilst keeping the alignment within a safe range

Aims

Robotic arm-assisted surgery offers accurate and reproducible guidance in component positioning and assessment of soft-tissue tensioning during knee arthroplasty, but the feasibility and early outcomes when using this technology for revision surgery remain unknown. The objective of this study was to compare the outcomes of robotic arm-assisted revision of unicompartmental knee arthroplasty (UKA) to total knee arthroplasty (TKA) versus primary robotic arm-assisted TKA at short-term follow-up.

Purpose:. Differences in the sizes of femoral and tibial components between females and males, between osteoarthritis (OA) and rheumatoid arthritis (RA), and between measured bone resection and the gap control technique during TKA were assessed. Method:. 500 PS-TKAswith the Stryker NRG system in 408 cases were assessed. There were 83 male knees and 417 female knees, and 472 OA knees and 28 RA knees. This study was performed in Japan, and almost all OA knees had varus deformities. In each case, the sizes of the femoral and tibial components were measured on radiographs. The measured sizes represented those of the measured bone resection. TKA was performed by the gap control technique using a tensor/balancer with 30 inch-pounds expansion strength, and the sizes of the femoral and tibial components (used size) were recorded. Results:. The measured size was the same for the femoral and tibial components in 80.6% of females. The measured size of the tibial component was larger than the femoral size in 42.2% and the same in 53.0% of males. The used size of the femoral component was larger than the measured size in 43.6%, and it was the same in 43.6% of all cases. The used size of the tibial component was smaller than the measured size in 42.2%, and it was the same as the measured size in 53.4% of OA cases. The used size of the tibial component was the same as the measured size in 75.0% of RA cases. The used size of the femoral component was larger than the used size of the tibial component in 65.6% of all cases. These results showed that: the tibial condyle is larger than the femoral condyle in males; a larger size of the femoral component than the tibial component was used in the gap control technique; the used size of the tibial component was the same as the measured size in RA knees; and the used size of the tibial component was smaller than the measured size in OA knees. Discussion:. During PS-TKA, the PCL is resected and the flexion gap is enlarged when the tensor/balancer is applied. Therefore, the size of the femoral component is larger with the gap control technique than with measured bone resection. In varus knees in Japan, the proximal articular surface shifts medially from the central line of the tibial shaft. Therefore, when the tibial component is set based on the central line of the tibial shaft, the medial condyle edge is not covered by the tibial component and is resected. A smaller size of the tibial component is used with this method. On the other hand, RA knees have no varus deformity, and the size of the femoral component was the same for the gap control technique and measured bone resection. The sizes of the femoral and tibial components in PS-TKA differ between the sexes, between OA and RA, and between measured bone resection and the gap control technique

Aims. The aim of this study was to investigate the local recurrence rate at an extended follow-up in patients following navigated resection of primary pelvic and sacral tumours. Patients and Methods. This prospective cohort study comprised 23 consecutive patients (nine female, 14 male) who underwent resection of a primary pelvic or sacral tumour, using computer navigation, between 2010 and 2012. The mean age of the patients at the time of presentation was 51 years (10 to 77). The rates of local recurrence and mortality were calculated using the Kaplan–Meier method. Results. Bone resection margins were all clear and there were no bony recurrences. At a mean follow-up for all patients of 59 months (12 to 93), eight patients (34.8%) developed soft-tissue local recurrence, with a cumulative rate of local recurrence at six-years of 35.1% (95% confidence interval (CI) 19.3 to 58.1). The cumulative all-cause rate of mortality at six-years was 26.1% (95% CI 12.7 to 49.1). Conclusion. Despite the positive early experience with navigated-assisted resection, local recurrence rates remain high. With increasing knowledge of the size of soft-tissue margins required to reduce local recurrence and the close proximity of native structures in the pelvis, we advise against compromising resection to preserve function, and encourage surgeons to reduce local recurrence by prioritizing wide resection margins of the tumour. Cite this article: Bone Joint J 2019;101-B:484–490

Proximal femoral replacements are commonly used in oncologic limb salvage procedures. Recently, these megaprostheses have been utilized in complex revision arthroplasties where proximal femoral bone is compromised. The purpose of this study is to evaluate the clinical and radiographic survivorship of proximal femoral replacements as a salvage treatment for bone loss after hip arthroplasty. We retrospectively reviewed the clinical and radiographic outcomes of 31 proximal femoral replacements of a single design between 2004 and 2013 at a single institution. The mean age at time of index surgery was 62 years, 58% were female, and mean BMI was 28.1 Kg/m. 2. The indications and complications associated with megaprosthesis implantation were collected. Average follow-up was 60 months (range 24–120 months). Kaplan-Meier survivorship assessed clinical and radiographic survivorship. Indication for revision, use of a constrained liner and construct length were assessed as risk factors for construct failure. The indications for proximal femoral replacement were periprosthetic infection (n=12, 38.7%), aseptic loosening (n=10, 32.3%), periprosthetic fracture (n=6, 19.3%), and non-union (n=3, 9.7%). A constrained liner was used in 22 hips (71%). The average length of bone resection was 148 cm (range 81–240 cm). There were nine revisions (29.2%): 3 for infection (9.7%) 2 for dislocation (6.5%), 2 for aseptic loosening (6.5%), and 2 for periprosthetic fracture (6.5%). Two of the 3 infections were in patients treated for infection. Overall survivorship was at 70.8%. There was no relation between the length of the bone resection, indication for revision and failure rate. Proximal femoral replacement in non-oncologic revision hip arthroplasty demonstrated a high failure rate at 2–10 year follow-up. Despite the high failure rate, the benefits of this salvage construct are that they allow full weight-bearing and allow rapid mobilization with minimal morbidity

Aims

The aim of this study was to determine the prevalence and impact of tourniquet use in patients undergoing limb salvage surgery with endoprosthetic reconstruction for a tumour around the knee.

Aims

The aims of this study were: 1) to describe extended restricted kinematic alignment (E-rKA), a novel alignment strategy during robotic-assisted total knee arthroplasty (RA-TKA); 2) to compare residual medial compartment tightness following virtual surgical planning during RA-TKA using mechanical alignment (MA) and E-rKA, in the same set of osteoarthritic varus knees; 3) to assess the requirement of soft-tissue releases during RA-TKA using E-rKA; and 4) to compare the accuracy of surgical plan execution between knees managed with adjustments in component positioning alone, and those which require additional soft-tissue releases.

Background. Mechanical alignment (MA) techniques for total knee arthroplasty (TKA) introduce significant anatomic modifications and secondary ligament imbalances. A restricted kinematic alignment (rKA) protocol was proposed to minimize these issues and improve TKA clinical results. Method. rKA tibial and femoral bone resections were simulated on 1000 knee CT-Scans from a database of patients undergoing TKA. rKA is defined by the following criteria: Independent tibial and femoral cuts within ± 5° of the bone neutral mechanical axis and; a resulting HKA within ±3° of neutral. Medial-lateral (ΔML) and flexion-extension (ΔFE) gap differences were calculated and compared with measured resection MA results. Results. Extension space ML imbalances ≥3mm occurred in 33% of TKA with MA technique versus 8% with rKA, and ≥5mm were present in up to 11% of MA knees versus 1% rKA (p<0.001). Using the MA technique, for the flexion space, higher ML imbalance rates were created by both MA techniques (using TEA or 3°PC) versus rKA (p<0.001). When all the differences between ΔML and ΔFE are considered together: using MA with TEA there were 41% of the knees with <3mm imbalances throughout; using PC this was 55% and using rKA it was 92% (p<0.001). Conclusion. Significantly less ML or FE gap imbalances are created using rKA versus MA for TKA. Using rKA may help the surgeon to preserve native knee ligament balance during TKA and avoid residual instability, whilst keeping the lower limb alignment within a safe range

Aims

This study aimed to analyze the accuracy and errors associated with 3D-printed, patient-specific resection guides (3DP-PSRGs) used for bone tumour resection.

Aims

To evaluate mid-to long-term patient-reported outcome measures (PROMs) of endoprosthetic reconstruction after resection of malignant tumours arising around the knee, and to investigate the risk factors for unfavourable PROMs.

Orthopaedic surgeons are currently faced with an overwhelming number of choices surrounding total knee arthroplasty (TKA), not only with the latest technologies and prostheses, but also fundamental decisions on alignment philosophies. From ‘mechanical’ to ‘adjusted mechanical’ to ‘restricted kinematic’ to ‘unrestricted kinematic’ — and how constitutional alignment relates to these — there is potential for ambiguity when thinking about and discussing such concepts. This annotation summarizes the various alignment strategies currently employed in TKA. It provides a clear framework and consistent language that will assist surgeons to compare confidently and contrast the concepts, while also discussing the latest opinions about alignment in TKA. Finally, it provides suggestions for applying consistent nomenclature to future research, especially as we explore the implications of 3D alignment patterns on patient outcomes.

Cite this article: Bone Joint J 2023;105-B(2):102–108.

Summary Statement. A prospective randomised evaluation of primary TKA utilizing patient specific instruments demonstrated great accuracy of bone resection, improved sagittal alignment and the potential to improve functional outcomes and reduce operating room costs when compared to standard TKA instrumentation. Introduction. Patient specific instruments (PSI), an alternative to standard total knee arthroplasty (TKA) technology, have been proposed to improve the accuracy of TKA implant placement and post-operative limb alignment. Previous studies have shown mixed results regarding the effectiveness of PSI. The purposes of this study were (1) to evaluate the accuracy of the pre-operative predicted PSI plan compared to intra-operative TKA resection measurements, (2) to compare patient-reported outcome measures of PSI and standard TKA patients, and (3) to compare the incremental cost savings with PSI. Patients and Methods. This randomised, prospective pilot study of 19 patients undergoing primary TKA with a cruciate-retaining cemented prosthesis (NexGen, Zimmer Inc.) was conducted by a single high-volume arthroplasty surgeon (DCA). Patients were randomised to PSI or standard instrumentation. Patients randomised to the PSI cohort received a pre-operative knee MRI for PSI fabrication using Zimmer proprietary software. 10 standard TKA and 9 PSI TKA were completed. Pre-operative baseline SF-36 and WOMAC scores were collected. Operative data collected included operating room times, implant details, femoral (medial/lateral distal and posterior) and tibial (medial/lateral) cut thicknesses, and number of instrument trays used. Hospitalization data collected included length of stay, blood loss, drain output, and transfusion requirements. Follow-up occurred at 2 weeks, 6–8 weeks, 3 months, 6 months, and 1 year, with SF-36 and WOMAC scores collected at each time point. Routine radiographic analysis was carried out in both cohorts. Extensive financial data was collected including costs of operating room use and anesthesia, implants, and hospitalization. Statistical analyses included t-tests for continuous variables and chi-square tests for categorical variables. Results. All femoral and tibial implant sizes used during TKA matched the component sizes predicted by the PSI software. Flexion gap bone resection (posterior medial/lateral femoral cuts) was extremely accurate (<1 mm on average) when compared with PSI predictions. PSI proximal tibial bone resection was also extremely accurate and within 1 mm on average of predicted values. Sagittal plane tibial component posterior slope in PSI TKA was significantly more accurate (7.33 degrees) in comparison to standard instrumentation (4.20 degrees) (p<0.025). No significant differences in coronal mechanical limb alignment existed between the two cohorts (p>0.05). There were no differences in operating room times, length of stay, or transfusions between the two groups. PSI patients used 4 fewer instrument trays per case (p<0.0001). There were no significant differences in functional outcome scores between the two groups (p>0.05). Discussion/Conclusion. PSI TKA demonstrated outstanding accuracy in bone resection when compared with the custom operative plan. There was no difference in post-operative coronal limb alignment or individual component alignment between the two groups, but an improvement in tibial component alignment in the sagittal plane in the PSI cohort was statistically significant. The number of instrument trays in PSI TKA's were significantly less than standard TKA which led to less cost for instrument sterilization and assembly, and quicker room set-up. PSI instrumentation resulted in accurate bone resection and appropriate limb and component alignment after primary TKA in this prospective randomised evaluation

Introduction. Surgeons performing a total knee replacement (TKR) have two available techniques available to help them achieve the proper bone resections and ligament tension – gap balancing (GB) and measured resection (MR). GB relies on balancing ligaments prior to bony resections whereas bony resections are made based on anatomical landmarks in MR. Many studies have been done to compare the joint kinematics between the two techniques, however the results have been varied. These studies were not done with anatomically designed prostheses. The Journey II (Smith & Nephew, Memphis, TN) is one such design which attempts to mimic the normal knee joint structure to return more natural kinematics to the joint, with emphasis on eliminating both paradoxical anterior motion and reduced posterior femoral rollback. Given the design differences between anatomical and non-anatomical prostheses, it is important to investigate whether one technique provides superior kinematics when an anatomical design is used. We hypothesize that there will be no difference between the two techniques. Methods. A total of 56 individuals were recruited to receive a Journey II prosthesis and randomized evenly to groups where the GB technique or MR technique is used. For all patients in the study, a series of radiostereometric analysis (RSA) images were acquired at 3-months post-operatively at different knee flexion angles, ranging in 20° increments from 0° to 120°. Model-based RSA software (RSACore, Leiden, Netherlands) was used to obtain the 3D positions and orientations of the femoral and tibial implant components, which were in turn used to obtain kinematic measures (contact locations and magnitude of excursion) for each condyle. Results. Preliminary results for the anterior-posterior (AP) contact locations from 33 patients (18 GB, 15 MR) are displayed in Figure 1. There were no significant differences in medial and lateral contact locations between the GB and MR groups for all angles of flexion. However, the pattern of medial contact for the MR technique displays more paradoxical anterior motion at mid-flexion (40°–60°) than the GB group. There were no significant differences in magnitude of excursion between groups on both medial (mean difference=1.96 mm, p=0.16) and lateral (mean difference=0.21 mm, p=0.79) condyles, indicating that posterior femoral rollback is similar between groups. Conclusions. Early results suggest that the MR technique is associated with slightly more abnormal kinematics than the GB technique when an anatomical prosthesis design is used for TKR. The GB technique may be more appropriate than MR technique for implanting anatomically designed knee replacements. For any figures or tables, please contact authors directly

Aim. Intramedullary osteomyelitis remains a challenge in the treatment of bone infections, requires organized, sequential and effective management to prevent its spread and subsequent recurrence. Errors are often made in the comprehensive treatment of this type of infection classified as type 1 of Cierny-Mader, where you can perform an insufficient treatment or in some cases perform very extensive and unnecessary bone resections. A rigorous protocol is proposed, by stages to achieve the total eradication of the infection and a surgical tactic that avoids diffusion of the infection or recurrences. Method. In the prospective case series study, 16 patients with type 1 intramedullary infection of Cierny Mader, diagnosed by radiology, TAC or MRI were included. The microbiological protocol is carried out, with the germ typing and the corresponding antibiogram, at least 3 samples of deep tissues, the biofilm and segments of dead bone are taken. In the surgical tactic, intramedullary sequestrations are resected, the intramedullary canal is cleaned by stages, initially in the most inflammatory focus detected, the medullary canal is accessed through a planned and defined bone window, with round edges to avoid fractures and allowing access To the flexible reamer and cleaning guides, an additional window is made that avoids the blood dissemination of the infection, the septic embolisms or the contamination of the underlying soft tissues. It is defined if it requires stabilization of the bone with internal or external devices, therapies are applied locally to avoid recolonization, using Bioglass or absorbable substitutes with selective antibiotic. The treatment is associated with intravenous antibiotic therapy between 2 and 6 weeks according to the type of germ and if it is multiresistant. It guarantees skin coverage and protection of structures at risk such as nerves, tendons and exposed bone. Results. Successful treatment results are obtained, infection eradication in 100% of cases, the healing of osteomyelitis is achieved by applying an integral management of the intramedullary canal Osteomyelitis and a complete protocol is established. Conclusions. The tactic and surgical technique applied in the integral management of intramedullary bone infection is essential to obtain definitive results in the eradication of bone infection. Care must be taken that the debridement is complete of the intramedullary canal and additionally, segmental or exaggerated resection of viable bone must be avoided, which survives and heals after the integral management of the infection with effective antibiotic therapy

Aim. Post traumatic distal tibia osteomyelitis (DTOM) with an upper ankle joint involvement is a serious complication after primary osteosynthesis and can be a nightmare for the patient and the surgeon as well. Our aim was to identify mayor complications during treatment and to find the way to prevent or treat them. Method. It is a retrospective analysis of eight patients with DTOM and an upper ankle joint involvement treated in our institution from 2012 to 2018. The average size of a bone defect after a debridement was 9 centimeters (4–15). Patients were treated in two stages. First stage was segmental bone resection, external fixation and soft tissue envelope reconstruction if necessary. At second stage a distraction frame was applied and proximal corticotomy performed. In all but one case a circular frame was used. Results. We have had one major intra-operative complication, an injury of arteria tibialis posterior during the corticotomy procedure. Except in one patient we did not observe major problems with pin-track infections. Despite bone-grafting in all patients, we observed three nonunions of docking site. We treated them by external fixator in two and retrograde intramedullar nail in one case. In two patient the distraction callus was weak. We had to bone graft and secure the callus with a plate in one and use a retrograde reamed intramedullar nail in second patient. We have observed two callus fracture after removal of the frame. A surgery was needed for both because of the deformation. The first patient was treated by new external frame, the second by retrograde reamed intramedullar nail. Conclusions. Callus distraction is a valuable option to treat a bone defect. The procedure has many possible problems and complications, especially during treatment of defects larger than six centimeters. It is very difficult for patients to tolerate a frame more than one year. We have found the use of an intramedullar tibial nail inserted in a retrograde way as a helpful option not just to shorten the time of external frame, but in combination with reaming also to accelerate the healing of the distraction callus and the upper ankle joint arthrodesis as well

Objectives. The aim of this study was to determine the polyethylene wear rate of Phase 3 Oxford Unicompartmental Knee Replacement bearings and to investigate the effects of resin type and manufacturing process. Methods. A total of 63 patients with at least ten years’ follow-up with three bearing types (1900 resin machined, 1050 resin machined, and 1050 resin moulded) were recruited. Patients underwent full weight-bearing model-based radiostereometric analysis to determine the bearing thickness. The linear wear rate was estimated from the change in thickness divided by the duration of implantation. Results. The wear rate for 1900 resin machined (n = 19), 1050 machined (n = 21), and 1050 moulded bearings (n = 23) were 60 µm/year (. sd. 42), 76 µm/year (. sd. 32), and 57 µm/year (. sd. 30), respectively. There was no significant difference between 1900 machined and 1050 machined (p = 0.20), but 1050 moulded had significantly less wear than the 1050 machined (p = 0.05). Increasing femoral (p < 0.001) and tibial (p < 0.001) component size were associated with increasing wear. Conclusion. Wear rate is similar with 1050 and 1900 resin, but lower with moulded bearings than machined bearings. The currently used Phase 3 bearings wear rate is low (1050 moulded, 57 µm/year), but higher than the previously reported Phase 2 bearings (1900 moulded, 20 µm/year). This is unlikely to be due to the change in polyethylene but may relate to the minimally invasive approach used with the Phase 3. This approach, as well as improving function and thus increasing activity levels, may increase the risk of surgical errors, such as impingement or bearing overhang, which can increase wear. Surgeons should aim to use 4 mm thick bearings rather than 3 mm thick bearings in young patients, unless they are small and need conservative bone resections. Cite this article: Bone Joint Res 2019;8:535–543

The October 2023 Oncology Roundup³⁶⁰ looks at: Are pathological fractures in patients with osteosarcoma associated with worse survival outcomes?; Spotting the difference: how secondary osteosarcoma manifests in retinoblastoma survivors versus conventional cases; Accuracy of MRI scans in predicting intra-articular joint involvement in high-grade sarcomas around the knee; Endoprosthetic reconstruction for lower extremity soft-tissue sarcomas with bone involvement; Local relapse of soft-tissue sarcoma of the extremities or trunk wall operated on with wide margins without radiation therapy; 3D-printed, custom-made prostheses in patients who had resection of tumours of the hand and foot; Long-term follow-up for low-grade chondrosarcoma; Evaluation of local recurrence and diagnostic discordance in chondrosarcoma patients undergoing preoperative biopsy; Radiological scoring and resection grade for intraosseous chondrosarcoma.

Abstract

Robotic-assisted total knee arthroplasty (TKA) has proven higher accuracy, fewer alignment outliers, and improved short-term clinical outcomes when compared to conventional TKA. However, evidence of cost-effectiveness and individual superiority of one system over another is the subject of further research. Despite its growing adoption rate, published results are still limited and comparative studies are scarce. This review compares characteristics and performance of five currently available systems, focusing on the information and feedback each system provides to the surgeon, what the systems allow the surgeon to modify during the operation, and how each system then aids execution of the surgical plan.

Cite this article: Bone Jt Open 2023;4(1):13–18.

Aims

The surgical helmet system (SHS) was developed to reduce the risk of periprosthetic joint infection (PJI), but the evidence is contradictory, with some studies suggesting an increased risk of PJI due to potential leakage through the glove-gown interface (GGI) caused by its positive pressure. We assumed that SHS and glove exchange had an impact on the leakage via GGI.

Introduction. Valgus deformity in an end stage osteoarthritic knee can be difficult to correct with no clear consensus on case management. Dependent on if the joint can be reduced and the degree of medial laxity or distension, a surgeon must use their discretion on the correct method for adequate lateral releases. Robotic assisted (RA) technology has been shown to have three dimensional (3D) cut accuracy which could assist with addressing these complex cases. The purpose of this work was to determine the number of soft tissue releases and component orientation of valgus cases performed with RA total knee arthroplasty (TKA). Methods. This study was a retrospective chart review of 72 RATKA cases with valgus deformity pre-operatively performed by a single surgeon from July 2016 to December 2017. Initial and final 3D component alignment, knee balancing gaps, component size, and full or partial releases were collected intraoperatively. Post-operatively, radiographs, adverse events, WOMAC total and KOOS Jr scores were collected at 6 months, 1 year and 2 year post-operatively. Results. Pre-operatively, knee deformities ranged from reducible knees with less than 5mm of medial laxity to up to 12° with fixed flexion contracture. All knees were corrected within 2.5 degrees of mechanical neutral. Average femoral component position was 0.26. o. valgus, and 4.07. o. flexion. Average tibial component position was 0.37. o. valgus, and 2.96. o. slope, where all tibial components were placed in a neutral or valgus orientation. Flexion and extension gaps were within 2mm (mean 1mm) for all knees. Medial and lateral gaps were balanced 100% in extension and 93% in flexion. The average flexion gap was 18.3mm and the average extension gap was 18.7mm. For component size prediction, the surgeon achieved their planned within one size on the femur 93.8% and tibia 100% of the time. The surgeon upsized the femur in 6.2% of cases. Soft tissue releases were reported in one of the cases. At latest follow-up, radiographic evidence suggested well seated and well fixed components. Radiographs also indicated the patella components were tracking well within the trochlear groove. No revision and re-operation is reported. Mean WOMAC total scores were improved from 24±8.3 pre-op to 6.6±4.4 2-year post-op (p<0.01). Mean KOOS scores were improved from 46.8±9.7 pre-op to 88.4±13.5 2-year post-op (p<0.01). Discussion. In this retrospective case review, the surgeon was able to balance the knee with bone resections and avoid disturbing the soft tissue envelope in valgus knees with 1–12° of deformity. To achieve this balance, the femoral component was often adjusted in axial and valgus rotations. This allowed the surgeon to open lateral flexion and extension gaps. While this study has several limitations, RATKA for valgus knees should continue to be investigated. For any figures or tables, please contact authors directly

Introduction. Robotic TKA allows for quantifiable precision performing bone resections for implant realignment within acceptable final component and limb alignments. One of the early steps in this robotic technique is after initial exposure and removal of medial and lateral osteophytes, a “pose-capture” is performed with varus and valgus stress applied to the knee in near full extension and 90° of flexion to assess gaps. Component alignment adjustments can be made on the preoperative plan to balance the gaps. At this point in the procedure any posterior osteophytes will still be present, which could after removal change the flexion and extension gaps by 1–3mm. This must be taken into consideration, or changes in component alignment could result in over-correction of gaps can occur. Objective. The purpose of this study was to identify what effect the posterior osteophyte's size and location and their removal had on gap measurements between pose-capture and after bone cuts are made and gaps assessed during implant trialing. Methods. This was a retrospective, single center cohort study comparing 100 robotic-assisted TKAs. Preoperative computer tomography was assessed for the presence, size and location of posterior osteophytes. Robotic-assessed gaps at pose capture and trialing were collected. Paired t-tests, independent t-tests and Pearson's correlation were used to examine this relationship. Results. Posterior osteophytes were present in 87% of cases with 59.3% isolated to the posterior medial femoral condyle. In the sagittal plane, posterior medial femoral condyle (pMFC), posterior lateral femoral condyle (pLFC) and posterior tibial (pT) osteophytes measured 6.75 ± 2.7mm, 5.77 ± 2.8mm, and 6.52 ± 3.14mm respectively. There was a significant increase in medial (17.4 ± 2.7mm vs 19.7 ± 2.2mm, p<0.01) and lateral (19.2 ± 2.2mm vs 20.5 ± 1.9mm, p<0.01) extension gaps from pose-capture to trialing. There was no difference in the delta of medial extension gaps from pose-change to trialing for knees with pMFC osteophytes > or < 5mm (2.1 ± 2.3 mm vs 2.4 ± 2.1mm, p=0.56). Similarly, there was no difference in the change in lateral extension gaps from pose-capture to trialing for knees with lateral posterior osteophytes > or < 5mm (1.2 ± 2.0mm vs 1.73 ± 1.53mm, p = 0.37). There was no statistically significant correlation between medial or lateral osteophyte size and change in medial (r=0.12, p=0.27) or lateral (r=0.11, p=0.36) extension gaps respectively. Conclusion. While there is a significant change in robotically assessed gaps at pose-capture and trialing, this change is small, our study findings are not able to substantiate that it is solely due to the presence, size or location of posterior osteophytes. A post-hoc power analysis indicates that, in order to detect a difference in gap between pose-capture and trialing of 1mm, over 75 knees with and without posterior osteophytes would be needed

Aims

The Vantage Total Ankle System is a fourth-generation low-profile fixed-bearing implant that has been available since 2016. We aimed to describe our early experience with this implant.

Aims

The goal was to evaluate tibiofemoral knee joint kinematics during stair descent, by simulating the full stair descent motion in vitro. The knee joint kinematics were evaluated for two types of knee implants: bi-cruciate retaining and bi-cruciate stabilized. It was hypothesized that the bi-cruciate retaining implant better approximates native kinematics.

Aims

The standard of wide tumour-like resection for chronic osteomyelitis (COM) has been challenged recently by adequate debridement. This paper reviews the evolution of surgical debridement for long bone COM, and presents the outcome of adequate debridement in a tertiary bone infection unit.

Aims

Mid-level constraint designs for total knee arthroplasty (TKA) are intended to reduce coronal plane laxity. Our aims were to compare kinematics and ligament forces of the Zimmer Biomet Persona posterior-stabilized (PS) and mid-level designs in the coronal, sagittal, and axial planes under loads simulating clinical exams of the knee in a cadaver model.

Aims

This study compared patient-reported outcomes of three total knee arthroplasty (TKA) designs from one manufacturer: one cruciate-retaining (CR) design, and two cruciate-sacrificing designs, anterior-stabilized (AS) and posterior-stabilized (PS).

Aims

Total knee arthroplasty (TKA) with a highly congruent condylar-stabilized (CS) articulation may be advantageous due to increased stability versus cruciate-retaining (CR) designs, while mitigating the limitations of a posterior-stabilized construct. The aim was to assess ten-year implant survival and functional outcomes of a cemented single-radius TKA with a CS insert, performed without posterior cruciate ligament sacrifice.

Aims

Surgical reconstruction of deformed Charcot feet carries a high risk of nonunion, metalwork failure, and deformity recurrence. The primary aim of this study was to identify the factors contributing to these complications following hindfoot Charcot reconstructions.

Introduction. The objective of this study was to assess the effect of PCL resection on flexion-extension gaps, mediolateral soft tissue laxity, fixed flexion deformity (FFD), and limb alignment during posterior-stabilised total knee arthroplasty (TKA). Methods. This prospective study included 110 patients with symptomatic knee osteoarthritis undergoing primary robotic-arm assisted posterior-stabilised TKA. All operative procedures were performed by a single surgeon using a standard medial parapatellar approach. Optical motion capture technology with fixed femoral and tibial registration pins was used to assess gaps pre- and post-PCL resection in knee extension and 90 degrees knee flexion. This study included 54 males (49.1%) and 56 females (50.9%) with a mean age of 68 ± 6.2 years at time of surgery. Mean preoperative hip-knee-ankle deformity was 6.1 ± 4.4 degrees varus. Results. PCL resection increased the flexion gap more than the extension gap in the medial (2.4 ± 1.5mm vs 1.3 ± 1.0mm respectively, p<0.001) and lateral (3.3 ± 1.6mm vs 1.2 ± 0.9mm respectively, p<0.01) compartments. The gap differences following PCL resection created mediolateral laxity in flexion (gap difference: 1.1 ± 2.5mm, p<0.001) but not in extension (gap difference: 0.1 ± 2.1mm, p=0.51). PCL resection improved overall FFD (6.3 ± 4.4° preoperatively vs 3.1 ± 1.5° postoperatively, p<0.001). There was a strong positive correlation between preoperative FFD and change in FFD following PCL release (Pearson correlation coefficient = 0.81, p<0.001). PCL resection did not affect overall limb alignment (change in alignment: 0.2 ± 1.2 degrees valgus, p=0.60). Conclusion. PCL resection creates flexion-extension mismatch by increasing the flexion gap proportionally more than the extension gap. The increase in the lateral flexion gap is greater than the increase in medial flexion gap, which creates mediolateral laxity in flexion. Improvements in FFD following PCL resection are dependent on the degree of deformity prior to PCL resection. Bone resection, implant positioning, and periarticular soft tissue balancing should account for these changes in flexion-extension gaps, mediolateral laxity, and fixed flexion deformity following PCL resection in PS TKA. For figures, tables, or references, please contact authors directly

Introduction. Clinical outcomes for total knee arthroplasty (TKA) are especially sensitive to lower extremity alignment and implant positioning. 1. The use of computer-assisted orthopedic surgery (CAOS) can improve overall TKA accuracy. 2. This study assessed the accuracy of an image-free CAOS guidance system (Exactech GPS, Blue-Ortho, Grenoble, FR) used in TKA. Materials and methods:. A high-resolution 3D scanner (Comet L3D, Steinbichler, Plymouth, MI) was used to scan seven knee models (MITA, Medical Models, Bristol, UK) and collect pre-identified anatomical landmarks (see Figure 1) prior to using the models to simulate knee surgery. The image-free CAOS guidance system was then used to acquire the same landmarks. After adjusting the position and orientation of the cutting block to match the targets, bone resections were performed, and the knee models were re-scanned. The 3D scans made before and after the cuts were overlaid (see Figure 2) and the resection parameters calculated using the pre-identified anatomical landmark data and advanced software (XOV & XOR, RapidForm, Lakewood, CO and UG NX, Siemens PLM, Plano, TX). Data sets obtained from the 3D scanner were compared with data sets from the guidance system. Given the accuracy of the 3D scanner, its measurements were used as the baseline for assessing CAOS system error. Results:. The CAOS system bone resection measurement errors had an overall mean of less than 0.35 mm. The mean errors for joint angle measurement was less than 0.6° (see Table I). Even considering the ranges, errors were no more than 1 mm for all bone resection measurements and no more than 1° for all joint angle measurements. The low variability is also supported by small standard deviation values. Discussion/Conclusion:. To our knowledge, this is the first study to use a high-resolution 3D scanner to assess the accuracy of surgical cuts made with image-free CAOS system assistance. Determining precise landmarks using CAOS for TKA has been shown to be of critical importance. 3. For this reason, the anatomical landmarks used by the scanner and guidance system were carefully identified and prepared to ensure consistency. The study demonstrated that the evaluated image-free CAOS system was able to achieve a high level of in-vitro accuracy (small mean errors) as well as a high level of precision (small error variability) when making femoral and tibial bone resections during TKA

The kinematic alignment (KA) approach to total knee arthroplasty (TKA) has recently increased in popularity. Accordingly, a number of derivatives have arisen and have caused confusion. Clarification is therefore needed for a better understanding of KA-TKA. Calipered (or true, pure) KA is performed by cutting the bone parallel to the articular surface, compensating for cartilage wear. In soft-tissue respecting KA, the tibial cutting surface is decided parallel to the femoral cutting surface (or trial component) with in-line traction. These approaches are categorized as unrestricted KA because there is no consideration of leg alignment or component orientation. Restricted KA is an approach where the periarthritic joint surface is replicated within a safe range, due to concerns about extreme alignments that have been considered ‘alignment outliers’ in the neutral mechanical alignment approach. More recently, functional alignment and inverse kinematic alignment have been advocated, where bone cuts are made following intraoperative planning, using intraoperative measurements acquired with computer assistance to fulfill good coordination of soft-tissue balance and alignment. The KA-TKA approach aims to restore the patients’ own harmony of three knee elements (morphology, soft-tissue balance, and alignment) and eventually the patients’ own kinematics. The respective approaches start from different points corresponding to one of the elements, yet each aim for the same goal, although the existing implants and techniques have not yet perfectly fulfilled that goal.

Introduction. In total knee arthroplasty (TKA), component realignment with bone-based surgical correction (BBSC) can provide soft tissue balance and avoid the unpredictability of soft tissue releases (STR) and potential for more post-operative pain. Robotic-assisted TKA enhances the ability to accurately control bone resection and implant position. The purpose of this study was to identify preoperative and intraoperative predictors for soft tissue release where maximum use of component realignment was desired. Methods. This was a retrospective, single center study comparing 125 robotic-assisted TKAs quantitatively balanced using load-sensing tibial trial components with BBSC and/or STR. A surgical algorithm favoring BBSC with a desired final mechanical alignment of between 3° varus and 2° valgus was utilized. Component realignment adjustments were made during preoperative planning, after varus/valgus stress gaps were assessed after removal of medial and lateral osteophytes (pose capture), and after trialing. STR was performed when a BBSC would not result in knee balance within acceptable alignment parameters. The predictability for STR was assessed at four steps of the procedure: Preoperatively with radiographic analysis, and after assessing static alignment after medial and lateral osteophyte removal, pose capture, and trialing. Cutoff values predictive of release were obtained using receiver operative curve analysis. Results. STR was necessary in 43.5% of cases with medial collateral ligament (MCL) release being the most common. On preoperative radiographs, a medial tibiofemoral angle (mTFA) ≤177° predicted MCL release (AUC = 0.76. p< 0.01) while an mTFA ≥188° predicted ITB release (AUC = 0.79, p <0.01). Intraoperatively after removal of osteophytes, a robotically assessed mechanical alignment (MA) ≥8° varus predicted MCL release (AUC = 0.84. p< 0.01) while a MA ≥2° valgus (AUC = 0.89, p< 0.01) predicted ITB release. During pose-capture, in medially tight knees, an extension gap imbalance ≥2.5mm (AUC = 0.82, p <0.01) and a flexion gap imbalance ≥2.0mm (AUC = 0.78, p <0.01) predicted MCL release while in laterally tight knees, any extension or flexion gap imbalance >0 mm predicted ITB release (AUC = 0.84, p <0.01 and AUC = 0.82, p <0.01 respectively). During trialing, in medially tight knees, a medial>lateral extension load imbalance ≥18 PSI (AUC = 0.84. p< 0.01) and a flexion load imbalance ≥ 35 PSI (AUC = 0.83, p< 0.01) predicted MCL release while, in laterally tight knees, a lateral>medial extension load imbalance ≥3 PSI (AUC = 0.97, p< 0.01) or flexion load imbalance ≥ 9.5 PSI (AUC = 0.86, p< 0.01) predicted ITB release. Of all identified predictors, load imbalance at trialing had the greatest positive predictive value for STR. Conclusion. There are limitations to the extent that TKA imbalance that can be corrected with BBSC alone if one has a range of acceptable alignment parameters. The ability to predict STR improves from pose-capture to trialing stages during detection of load imbalance. Perhaps this may be due to posterior osteophytes that are still present at pose capture. Further investigation of the relationship between the presence, location and size of posterior osteophytes and need for STR during TKA is necessary

Clinical outcomes for total knee arthroplasty (TKA) are especially sensitive to lower extremity alignment and implant positioning. The use of computer-assisted orthopedic surgery (CAOS) can improve overall TKA accuracy. This study assessed the accuracy of an image-free CAOS guidance system (Exactech GPS, Blue-Ortho, Grenoble, FR) used in TKA. A high-precision 3D scanner (Comet L3D, Steinbichler, Plymouth, MI) was used to scan seven knee models (MITA, Medical Models, Bristol, UK) and collect pre-identified anatomical landmarks prior to using the models to simulate knee surgery. The Exactech GPS was then used to acquire the same landmarks. After adjusting the Exactech GPS cutting block to match the targets, bone resections were performed, and the knee models were re-scanned. The 3D scans made before and after the cuts were overlaid and the resection parameters calculated using the pre-identified anatomical landmark data and advanced software (XOV & XOR, RapidForm, Lakewood, CO and UG NX, Siemens PLM, Plano, TX). Data sets obtained from the 3D scanner were compared with data sets from the guidance system. Given the accuracy of the 3D scanner, its measurements were used as the baseline for assessing CAOS system error. The CAOS system bone resection measurement errors had an overall mean of less than 0.35 mm. The mean errors for joint angle measurement was less than 0.6°. Even considering the ranges, errors were no more than 1 mm for all bone resection measurements and no more than 1° for all joint angle measurements. The low variability is also supported by small SD values. To our knowledge, this is the first study to use a high-resolution 3D scanner to assess the accuracy of surgical cuts made with image-free CAOS system assistance. Determining precise landmarks using CAOS for TKA has been shown to be of critical importance. For this reason, the anatomical landmarks used by the scanner and guidance system were carefully identified and prepared to ensure consistency. The study demonstrated that the evaluated image-free CAOS system was able to achieve a high level of in-vitro accuracy (small mean errors) as well as a high level of precision (small error variability) when making femoral and tibial bone resections during TKA

There is a critical need for safe innovation in total joint replacements to address the demands of an ageing yet increasingly active population. The development of robust implant designs requires consideration of uncertainties including patient related factors such as bone morphology but also activity related loads and the variability in the surgical procedure itself. Here we present an integrated framework considering these sources of variability and its application to assess the performance of the femoral component of a total hip replacement (THR). The framework offers four key features. To consider variability in bone properties, an automated workflow for establishing statistical shape and intensity models (SSIM) was developed. Here, the inherent relationship between shape and bone density is captured and new meshes of the target bone structures are generated with specific morphology and density distributions. The second key feature is a virtual implantation capability including implant positioning, and bone resection. Implant positioning is performed using automatically identified bone features and flexibly defined rules reflecting surgical variability. Bone resection is performed according to manufacturer guidelines. Virtual implantation then occurs through Boolean operations to remove bone elements contained within the implant's volume. The third feature is the automatic application of loads at muscle attachment points or on the joint contact surfaces defined on the SSIM. The magnitude and orientation of the forces are derived from models of similar morphology for a range of activities from a database of musculoskeletal (MS) loads. The connection to this MS loading model allows the intricate link between morphology and muscle forces to be captured. Importantly, this model of the internal forces provides access to the spectrum of loading conditions across a patient population rather than just typical or average values. The final feature is an environment that allows finite element simulations to be run to assess the mechanics of the bone-implant construct and extract results for e.g. bone strains, interface mechanics and implant stresses. Results are automatically processed and mapped in an anatomically consistent manner and can be further exploited to establish surrogate models for efficient subsequent design optimization. To demonstrate the capability of the framework, it has been applied to the femoral component of a THR. An SSIM was created from 102 segmented femurs capturing the heterogeneous bone density distributions. Cementless femoral stems were positioned such that for the optimal implantation the proximal shaft axis of the femurs coincided with the distal stem axis and the position of the native femoral head centre was restored. Here, the resection did not affect the greater trochanter and the implantations were clinically acceptable for 10000 virtual implantations performed to simulate variability in patient morphology and surgical variation. The MS database was established from musculoskeletal analyses run for a cohort of 17 THR subjects obtaining over 100,000 individual samples of 3D muscle and joint forces. An initial analysis of the mechanical performance in 7 bone-implant constructs showed levels of bone strains and implant stresses in general agreement with the literature

Introduction. The purpose of this study was to experimentally evaluate impingement and dislocation of total hip replacements while performing dynamic movements under physiological-like conditions. Therefore, a hardware-in-the-loop setup has been developed, in which a physical hip prosthesis actuated by an industrial robot interacts with an in situ-like environment mimicked by a musculoskeletal multibody simulation-model of the lower extremity. Methods. The multibody model of the musculoskeletal system comprised rigid bone segments of the lower right extremity, which were mutually linked by ideal joints, and a trunk. All bone geometries were reconstructed from a computed tomography set preserving anatomical landmarks. Inertia properties were identified based on anthropometric data and by correlating bone density to Hounsfield units. Relevant muscles were modeled as Hill-type elements, passive forces due to capsular tissue have been neglected. Motion data were captured from a healthy subject performing dislocation-associated movements and were fed to the musculoskeletal multibody model. Subsequently, the robot moved and loaded a commercially available total hip prosthesis and closed the loop by feeding the physical contact information back to the simulation model. In this manner, a comprehensive parameter study analyzing the impact of implant position and design, joint loading, soft tissue damage and bone resection was implemented. Results. The parameter study revealed a generally high dislocation risk for the seating-to-rising with adduction scenarios. Improper implant positioning or design could be compensated by adjusting prosthesis components correspondingly. Gluteal insufficiency or lower joint loading did not result in higher impingement or dislocation risk. However, severe malfunction of the artificial joint was found for proximal bone resection. Discussion. Previous testing setups ignored the impact of active muscles or relied on simplified contact mechanics. Herein, total hip replacement stability has been investigated experimentally by using a hardware-in-the-loop simulation. Thereby, several influencing factors such as implant position and design as well as soft tissue insufficiency and imbalance could be systematically evaluated with the goal to enhance joint stability

Background. Intraoperative balancing can be accomplished by either more prevalent but less predictable soft tissue releases, implant realignment through adjustments of bone resection or a combination of both. There is no published study directly comparing these methods. Objective. To provide a direct comparison between implant realignment and traditional ligamentous release for soft tissue balancing in total knee arthroplasty using both objective kinematic sensor data to document final balance and patient reported outcomes. Methods. IRB Approved retrospective cohort study of prospectively collected data comparing kinematic sensor data and patient reported outcomes for all consecutive patients that underwent TKA utilizing kinematic sensors with or without robotic assistance performed between August 2012 to April 2017 to allow for a minimum of 12 months clinical follow up. Results. 107 knees met inclusion criteria. Component realignment was utilized more frequently in the robotic surgical technique cohort than the non-robotic, non-navigated cohort due to the increased precision in implant realignment possble. Although KSS and FJS scores showed equivalent outcomes at both the 3-month and 1-year time points, KSS-Function scores at 1-year showed a statistically and clinically significant increase of 11.89 points in the implant realignment cohort compared to the ligamentous release cohort. Conclusions. A statistically and clinically significant improvement in KSS-Function scores benefiting the implant realignment technique was seen at 1-year post-operatively. This may suggest a benefit to using implant realignment as the ideal balancing strategy in total knee arthroplasty. Further longitudinal studies with increased number of cases should increase statistical power which is needed to further confirm the suggested benefits of the implant realignment balancing technique

Objectives. Patient-specific (PS) implantation surgical technology has been introduced in recent years and a gradual increase in the associated number of surgical cases has been observed. PS technology uses a patient’s own geometry in designing a medical device to provide minimal bone resection with improvement in the prosthetic bone coverage. However, whether PS unicompartmental knee arthroplasty (UKA) provides a better biomechanical effect than standard off-the-shelf prostheses for UKA has not yet been determined, and still remains controversial in both biomechanical and clinical fields. Therefore, the aim of this study was to compare the biomechanical effect between PS and standard off-the-shelf prostheses for UKA. Methods. The contact stresses on the polyethylene (PE) insert, articular cartilage and lateral meniscus were evaluated in PS and standard off-the-shelf prostheses for UKA using a validated finite element model. Gait cycle loading was applied to evaluate the biomechanical effect in the PS and standard UKAs. Results. The contact stresses on the PE insert were similar for both the PS and standard UKAs. Compared with the standard UKA, the PS UKA did not show any biomechanical effect on the medial PE insert. However, the contact stresses on the articular cartilage and the meniscus in the lateral compartment following the PS UKA exhibited closer values to the healthy knee joint compared with the standard UKA. Conclusion. The PS UKA provided mechanics closer to those of the normal knee joint. The decreased contact stress on the opposite compartment may reduce the overall risk of progressive osteoarthritis. Cite this article: K-T. Kang, J. Son, D-S. Suh, S. K. Kwon, O-R. Kwon, Y-G. Koh. Patient-specific medial unicompartmental knee arthroplasty has a greater protective effect on articular cartilage in the lateral compartment: A Finite Element Analysis. Bone Joint Res 2018;7:20–27. DOI: 10.1302/2046-3758.71.BJR-2017-0115.R2

The December 2023 Oncology Roundup³⁶⁰ looks at: A single osteotomy technique for frozen autograft; Complications, function, and survival of tumour-devitalized autografts used in patients with limb-sparing surgery; Is liquid nitrogen recycled bone and vascular fibula the biological reconstruction of choice?; Solitary pulmonary metastases at first recurrence of osteosarcoma; Is a radiological score able to predict resection-grade chondrosarcoma in primary intraosseous lesions of the long bones?; Open versus core needle biopsy in lower-limb sarcoma – current practice patterns and patient outcomes; Natural history of intraosseous low-grade chondroid lesions of the proximal humerus; Local treatment modalities and event-free survival in patients with localized Ewing’s sarcoma; Awaiting biopsy results in solitary pathological proximal femoral fractures.

Background. Bone preservation is desired for future revision in any knee arthroplasty. There is no study comparing the difference in the amount of bone resection when soft tissue balance is performed with or without computer navigation. To determine the effect on bony cuts when soft tissue balance is performed with or without use of computer software by standard manual technique in total knee arthroplasty. One hundred patients aged 50 to 88 years underwent navigated TKR for primary osteoarthritis. In group A, 50 patients had both soft tissue release and bone cuts done using computer-assisted navigation. In group B, 50 patients had soft tissue release by standard manual technique first and then bone cuts were guided by computer-assisted navigation. In group A the mean medial tibial resection was 5 ± 2.3 mm and lateral was 8 ± 1 mm compared to 5 ± 2 mm (P = 0.100) and 8 ± 1 mm respectively in group B (P = 0.860). In group A the mean medial femoral bone cut was 9 ± 2.9 mm and lateral was 8 ± 2 mm as compared to 9.5 ± 2.9 mm (P = 0.316) and 10 ± 2.2 mm respectively in group B (P = 0.001). Average prosthesis size was 6 (range 3 to 8) in group A as compared to size 5 (range 2 to 7) in group B. Average navigation time in group A was 102 minutes (range 45 to 172) and in group B was 83 minutes (range 42 to 165, P = 0.031). Our results show that performing soft tissue release and bone cuts using computer- assisted navigation is more bone conserving as compared to manual soft tissue release and bone cuts using computer navigation for TKR, thus preserving bone for possible future revision surgery

Post-operative stability in a primary TKA procedure requires surgical skill in establishing symmetric flexion and extension spaces. Many surgeons further utilise techniques associated with “gap balancing” by attending to the dimensional space between the femur and tibia in developing flexion and extension gaps following bone resections and/or soft tissue releases. Questions still arise related to these gaps, in particular whether or not these gaps should be created dimensionally equal to each other by adjusting bone resections. Previous publications on this subject point to the conclusion that they are not dimensionally the same, but have a relationship to the supporting soft tissue in the flexion and extension positions. This study has been designed to investigate this premise. A soft tissue force sensing device, enabling the surgeon to create accurate balanced posterior femoral condylar resections relative to the soft tissues and the proximal tibia, has been integrated into the current surgical technique to create reliable flexion gap symmetry. To extend the concept of using balanced relative force readings to a more complete gap balancing technique, a preliminary distal femoral resection is made to facilitate mounting the adjustable instrument interfacing with the force sensor. Femoral rotation is adjusted to establish a symmetric flexion space based on balancing the relative force values in the tow femoral-tibial joint compartments. This sensor guided balancing step establishes the desired tibial insert thickness in the reconstructed knee. The final distal femoral bone resection is then made to equate the extension gap to the balanced flexion gap. Taking the concept of balanced resection to the next level, special angled inserts have been developed to fit onto the sensor and fill the extension space, in efforts to determine and create a balanced extension space. Data was gathered to relate the relative flexion force value to the resulting relative extension force value to see how this compares in a series of TKA’s. The results of this data will begin to shed light on the supporting soft tissue conditions when a true balanced resection technique is utilised. The focus of this study is to evaluate the extension forces resulting from this technique to better define a functional relationship between the flexion and extension gaps in the gap balancing technique

The management of bone loss in revision total knee replacement (TKA) remains a challenge. To accomplish the goals of revision TKA, the surgeon needs to choose the appropriate implant design to “fix the problem,” achieve proper component placement and alignment, and obtain robust short- and long-term fixation. Proper identification and classification of the extent of bone loss and deformity will aid in preoperative planning. Extensive bone loss may be due to progressive osteolysis (a mechanism of failure), or as a result of intraoperative component removal. The Anderson Orthopaedic Research Institute (AORI) is a useful classification system that individually describes femoral and tibial defects by the appearance, severity, and location of bone defects. This system provides a guideline to treatment and enables preoperative planning on radiographs. In Type 1 defects, femoral and tibial defects are characterised by minor contained deficiencies at the bone-implant interface. Metaphyseal bone is intact and the integrity of the joint line is not compromised. In this scenario, the best reconstruction option is to increase the thickness of bone resection and to fill the defect with cancellous bone graft or cement. Type 2 defects are characterised by deficient metaphyseal bone involving one or more femoral condyle(s) or tibial plateau(s). The peripheral rim of cortical bone may be intact or partially compromised, and the joint line is abnormal. Reconstruction options for a Type 2A defect include impaction bone grafting, cement, or more commonly, prosthetic augmentation (e.g. sleeves, augments or wedges). In Type 2B defects, metaphyseal bone of both femoral condyles or both tibial plateaus is deficient. The peripheral rim of cortical bone may be intact or partially compromised, and the joint line is abnormal. Options for a Type 2B defect include impaction grafting, bulk structural allograft, prosthetic augmentation, metaphyseal sleeves (in some cases), or metaphyseal cones. Finally, in the presence of a Type 3 deficiency, both metaphyseal and cortical bone is deficient and there is partial or complete disruption of the collateral ligament attachments. In this case, the most commonly used reconstruction options include hinged implants or megaprostheses with or without bulk structural allograft, prosthetic augmentation, and/or metaphyseal/diaphyseal sleeves or cones. Today, we are fortunate to have a wide variety of options available to aid in reconstruction of a revision TKA with massive bone loss. Historically, use of cement, bone grafting, or use of a tumor-type or hinged implant were considered the main options for reconstruction. The development and adoption of highly porous sleeves and cones has given the surgeon a new and potentially more durable option for reconstruction of previously difficult to treat defects. Using radiographs and computed tomography, surgeons are able to preoperatively classify bone loss and anticipate a reconstruction plan based upon the classification; however, it is always important to have several back-up options on hand during revision surgery in the event bone loss is worse than expected

Introduction and Aims: A significant proportion of patients currently undergoing total knee arthroplasty have uni-compartmental disease. Unicondylar knee replacement (UKA) offers the benefits of less bone resection and better soft tissue retention. However, knee kinematic changes after UKA have not been established. Method: A significant proportion of patients currently undergoing total knee arthroplasty have uni-compartmental disease. Unicondylar knee replacement (UKA) offers the benefits of less bone resection and better soft tissue retention. However, knee kinematic changes after UKA have not been established. Results: In the normal knee, knee flexion was accompanied by femoral rollback and tibial internal rotation. Similar patterns of rollback and rotation were seen after UKA. Surprisingly, resecting the ACL did not affect rollback or tibial rotation. However, tibial rotation was significantly different and was more variable after TKA. This suggests that loss of the ACL may not be the major cause of abnormal kinematics after TKA. Conclusion: Abnormal kinematics have been previously reported after TKA. However, UKA appeared to maintain normal kinematics. This study reported kinematic advantages to UKA, in addition to less bone resection and better recovery

Aims

One-stage revision hip arthroplasty for periprosthetic joint infection (PJI) has several advantages; however, resection of the proximal femur might be necessary to achieve higher success rates. We investigated the risk factors for resection and re-revisions, and assessed complications and subsequent re-revisions.

The etiology of the flexion contracture is related to recurrent effusions present in a knee with end-stage degenerative joint disease secondary to the associated inflammatory process. These recurrent effusions cause increased pressure in the knee causing pain and discomfort. Patients will always seek a position of comfort, which is slight flexion. Flexion decreases the painful stimulus by reducing pressure in the knee and relaxing the posterior capsule. Unfortunately, this self-perpetuating process leads to a greater degree of contracture as the disease progresses. Furthermore, patients rarely maintain the knee in full extension. Even during the gait cycle the knee is slightly flexed. As their disease progresses, patients limit their ambulation and are more frequently in a seated position. Patients often report sleeping with a pillow under their knee or in the fetal position. All of these activities increase flexion contracture deformity. Patients with excessive deformity >40 degrees should be counseled regarding procedural complexity and that increasing constraint may be required. Patients are seen preoperatively by a physical therapist and given a pre-arthroplasty conditioning program. Patients with excessive flexion contracture are specifically instructed on stretching techniques, as well as quadriceps rehabilitation exercises. The focus in the postoperative physiotherapy rehabilitation program continues toward the goal of full extension. Patients are instructed in appropriate stretching regimes. Patients are immobilised for the first 24 hours in full extension with plaster splints, such as with a modified Robert Jones dressing. This dressing is removed on postoperative day one. The patient is then placed in a knee immobiliser and instructed to wear it at bed rest, during ambulation and in the evening, only removing for ROM exercises. In cases of severe flexion deformity >30 degrees, patients are maintained in full extension for 3–4 weeks until ROM is begun. Patients are encouraged to use a knee immobiliser for at least the first 6 weeks postoperatively. Treating patients with flexion contracture involves a combination of bone resection and soft tissue balance. One must make every effort to preserve both the femoral and tibial joint line. In flexion contracture the common error is to begin by resecting additional distal femur, which may result in joint line elevation and mid-flexion instability. The distal femoral resection should remove that amount of bone being replaced with metal. Attention should be directed at careful and meticulous balance of the soft tissues and release of the contracted posterior capsule with re-establishment of the posterior recess, which will correct the majority of flexion contractures. Inability to achieve ROM after TKA represents a frustrating complication for both patient and surgeon. Non-operative treatments for the stiff TKA include shoe lift in contralateral limb, stationery bicycle with elevated seat position, extension bracing, topical application of hand-held instruments to areas of soft tissue-dysfunction by a trained physical therapist over several outpatient sessions, and use of a low load stretch device. Manipulation under anesthesia is indicated in patients after TKA having less than 90 degrees ROM after 6 weeks, with no progression or regression in ROM. Other operative treatments range from a downsizing exchange of the polyethylene bearing to revision with a constrained device and low-dose irradiation in cases of severe arthrofibrosis

Knee replacement is a proven and reproducible procedure to alleviate pain, re-establish alignment and restore function. However, the quality and completeness to which these goals are achieved is variable. The idea of restoring function by reproducing condylar anatomy and asymmetry has been gaining favor. As knee replacements have evolved, surgeons have created a set of principles for reconstruction, such as using the femoral transepicondylar axis (TEA) in order to place the joint line of the symmetric femoral component parallel to the TEA, and this has been shown to improve kinematics. However, this bony landmark is really a single plane surrogate for independent 3-dimensional medial and lateral femoral condylar geometry, and a difference has been shown to exist between the natural flexion-extension arc and the TEA. The TEA works well as a surrogate, but the idea of potentially replicating normal motion by reproducing the actual condylar geometry and its involved, individual asymmetry has great appeal. Great variability in knee anatomy can be found among various populations, sizes, and genders. Each implant company creates their specific condylar geometry, or “so called” J curves, based on a set of averages measured in a given population. These condylar geometries have traditionally been symmetric, with the individualised spatial placement of the (symmetric) curves achieved through femoral component sizing, angulation, and rotation performed at the time of surgery. There is an inherent compromise in trying to achieve accurate, individual medial and lateral condylar geometry reproduction, while also replicating size and avoiding component overhang with a set implant geometry and limited implant sizes. Even with patient-specific instrumentation using standard over-the-counter implants, the surgeon must input his/her desired endpoints for bone resection, femoral rotation, and sizing as guidelines for compromise. When all is done, and soft tissue imbalance exists, soft tissue release is the final, common compromise. The custom, individually made knee design goals include reproducible mechanical alignment, patient-specific fit and positioning, restoration of articular condylar geometry, and thereby, more normal kinematics. A CT scan allows capture of three-dimensional anatomical bony details of the knee. The individual J curves are first noted and corrected for deformity, after which they are anatomically reproduced using a Computer-Aided Design (CAD) file of the bones in order to maximally cover the bony surfaces and concomitantly avoid implant overhang. No options for modifications are offered to the surgeon, as the goal is anatomic restoration. Given these ideals, to what extent are patients improved? The concept of reproducing bony anatomy is based on the pretext that form will dictate function, such that normal-leaning anatomy will tend towards normal-leaning kinematics. Therefore, we seek to evaluate knee function based on objective assessments of movement or kinematics. In summary, the use of custom knee technology to more closely reproduce an individual patient's anatomy holds great promise in improving the quality and reproducibility of postoperative function. Compromises of fit and rotation are minimised, and implant overhang is potentially eliminated as a source of pain. Early results have shown objective improvements in clinical outcomes. Admittedly, this technology is limited to those patients with mild to moderate deformity at this time, since options like constraint and stems are not available. Yet these are the patients who can most clearly benefit from a higher functional state after reconstruction. Time will reveal if this potential can become a reproducible reality

Objectives. Up to 40% of unicompartmental knee arthroplasty (UKA) revisions are performed for unexplained pain which may be caused by elevated proximal tibial bone strain. This study investigates the effect of tibial component metal backing and polyethylene thickness on bone strain in a cemented fixed-bearing medial UKA using a finite element model (FEM) validated experimentally by digital image correlation (DIC) and acoustic emission (AE). Materials and Methods. A total of ten composite tibias implanted with all-polyethylene (AP) and metal-backed (MB) tibial components were loaded to 2500 N. Cortical strain was measured using DIC and cancellous microdamage using AE. FEMs were created and validated and polyethylene thickness varied from 6 mm to 10 mm. The volume of cancellous bone exposed to < -3000 µε (pathological loading) and < -7000 µε (yield point) minimum principal (compressive) microstrain and > 3000 µε and > 7000 µε maximum principal (tensile) microstrain was computed. Results. Experimental AE data and the FEM volume of cancellous bone with compressive strain < -3000 µε correlated strongly: R = 0.947, R. 2. = 0.847, percentage error 12.5% (p < 0.001). DIC and FEM data correlated: R = 0.838, R. 2. = 0.702, percentage error 4.5% (p < 0.001). FEM strain patterns included MB lateral edge concentrations; AP concentrations at keel, peg and at the region of load application. Cancellous strains were higher in AP implants at all loads: 2.2- (10 mm) to 3.2-times (6 mm) the volume of cancellous bone compressively strained < -7000 µε. Conclusion. AP tibial components display greater volumes of pathologically overstrained cancellous bone than MB implants of the same geometry. Increasing AP thickness does not overcome these pathological forces and comes at the cost of greater bone resection. Cite this article: C. E. H. Scott, M. J. Eaton, R. W. Nutton, F. A. Wade, S. L. Evans, P. Pankaj. Metal-backed versus all-polyethylene unicompartmental knee arthroplasty: Proximal tibial strain in an experimentally validated finite element model. Bone Joint Res 2017;6:22–30. DOI:10.1302/2046-3758.61.BJR-2016-0142.R1

Introduction. Surgeons performing a total knee replacement (TKR) have two techniques to assist them achieve proper bone resections and ligament tension – gap balancing (GB) and measured resection (MR). GB relies on balancing ligaments prior to bony resections, whereas bony resections are made based on anatomical landmarks in MR. Many studies have been done to compare the implant migration and kinematics between the two techniques, but the results have been varied. However, these studies have not been done on modern anatomically designed prostheses using radiostereometric analysis (RSA). Anatomical designs attempt to mimic the normal knee joint structure to return more natural kinematics to the joint, with emphasis on eliminating both paradoxical anterior motion and reduced posterior femoral rollback. Given the major design differences between anatomical and non-anatomical prostheses, it is important to investigate whether one surgical technique may have advantages another. We hypothesize that there would be no difference between GB and MR techniques in implant migration, but that GB might provide better knee kinematics. Methods. Patients were recruited to receive an anatomically designed prosthesis and randomized to groups where the GB or MR technique is used. For all patients in the study, RSA images were acquired at a 2 week baseline, as well as at 6 weeks, 3 months, and 6 months post-operatively. These images were used to collect the maximum total point motion (MTPM) of the tibial and femoral implant components relative to the bone using a model-based RSA software. A series of RSA images were also acquired at 3-months post-operatively at different knee flexion angles, ranging in 20° increments from 0° to 100°. Model-based RSA software was used to obtain the 3D positions and orientations of the femoral and tibial components, which were used to obtain the anterior-posterior (AP) contact locations for each condyle. Results. Results from 47 patients (27 GB, 20 MR) were analyzed. No significant differences were present between the two surgical techniques for tibial component MTPM at 6 weeks (mean difference=0.02 mm, p=0.61), 3 months (mean difference=0.01 mm, p=0.92), and 6 months (mean difference=0.01 mm, p=0.93) post-operatively. No significant differences were present between the two surgical techniques for femoral component MTPM at 6 weeks (mean difference=0.12 mm, p=0.08), 3 months (mean difference=0.05 mm, p=0.54), and 6 months (mean difference=0.13 mm, p=0.05) post-operatively. On the medial condyle, no significant differences in AP contact location were found at all angles between 0° and 80° of flexion (p-values from 0.28 to 0.95). There was a significant difference medially between the AP contact location of the two surgical techniques at 100° of flexion (p=0.01), indicating more posterior rollback on the medial condyle in the GB technique. On the lateral condyle, no significant differences in AP contact location were found at all angles of flexion (p-values from 0.13 to 0.62). On the medial condyle of the GB group, the AP contact location moved posteriorly 5.83 mm from 0° to 20°, anteriorly 2.60 mm from 20° to 60°, and posteriorly 7.40 mm from 60° to 100°. On the medial condyle of the MR group, the AP contact location moved posteriorly 5.36 mm from 0° to 20°, anteriorly 2.87 mm from 20° to 60°, and posteriorly 3.65 mm from 60° to 100°. On the lateral condyle of the GB group, the AP contact location moved posteriorly 6.87 mm from 0° to 20°, 0.30 mm from 20° to 60°, and 3.61 mm from 60° to 100°. On the lateral condyle of the MR group, the AP contact location moved posteriorly 6.86 mm from 0° to 20°, anteriorly 0.02 mm from 20° to 60°, and posteriorly 3.56 mm from 60° to 100°. Conclusions. The GB and MR techniques are very similar in terms of implant migration and overall kinematics when an anatomical prosthesis design is used for TKR. This study suggests that surgeon preference should be used when deciding which technique to use for implanting this anatomically designed knee replacement. For figures, tables, or references, please contact authors directly

INTRODUCTION. Use of a novel ligament gap balancing instrumentation system in total knee arthroplasty (TKA) resulted in femoral component external rotation values which were higher on average, compared to measured bone resection systems. In one hundred twenty knees in 110 patients the external rotation averaged 6.9 degrees (± 2.8) and ranged from 0.6 to 12.8 degrees. The external rotation values in this study were 4° and 2° larger, respectively, than the typical 3° and 5° discrete values that are common to measured resection systems. The purpose of the present study was to determine the effect of these greater external rotation values for the femoral component on patellar tracking, flexion stability and function of two different TKA implant designs. METHODS. In the first arm of the study, 120 knees in 110 patients were consecutively enrolled by a single surgeon using the same implant design (single radius femur with a medial constraint tibial liner) across subjects. All patients underwent arthroplasty with tibial resection first and that set external rotation of the femoral component based upon use of a ligament gap balancing system. Following ligament tensioning / balancing, the femur was prepared. The accuracy of the ligament balancing system was assessed by reapplying equal tension to the ligaments using a tensioning bolt and torque wrench in flexion and extension after the bone resections had been made. The resulting flexion and extension gaps were then measured to determine rectangular shape and equality of the gaps. Postoperative Merchant views were obtained on all of the patients and patellar tracking was assessed and compared to 120 consecutive total knee arthroplasties previously performed by the same surgeon with the same implant using a measured resection system. In the second arm of the study, 100 unilateral knees in 100 patients were consecutively enrolled. The same instrumentation and technique by the same surgeon was used, but with a different implant design (single radius femur without a medial constraint tibial liner). RESULTS. Rectangular flexion and extension gaps were obtained within ± 0.5mm in all cases. Equality of the flexion and extension gaps was also obtained within ± 0.5mm in all cases. Merchant views of the total knee arthroplasties showed central patellar tracking with no tilt or subluxation in 90% of the ligament gap balanced knees and 74% of the measured resection knees. Arthrofibrosis resulting in a closed manipulation under anesthesia was required in 6% of the knees with single radius femurs and medial constaint tibial liners, but only in 1% of the single radius femur knees without medial constraint liners. DISCUSSION AND CONCLUSION. External rotation values are higher on average, when ligament tensioning / balancing is employed with this novel system compared to measured resection systems. In this study this resulted in consistent matching of the flexion gap to the extension gap and better patellar tracking. These findings suggest that limiting the surgeon to discrete rotation values may be at odds with where the femur “desires” to be, given soft tissue considerations for each patient. Also, even with ideal soft tissue balancing, TKA implant design can have a significant affect on the outcome measure of development of arthrofibrosis

Aim. Optimal strategies for surgical and antimicrobial management of Candida periprosthetic joint infections (PJI) are unclear. We present a retrospective case series of patients diagnosed with PJI caused by Candida spp. Method. Patients treated at our institution with Candida PJI from 01/2017 to 04/2018 were retrospectively included with isolation of Candida spp. in synovial fluid, intraoperative tissue or sonication fluid culture. PJI was defined by the proposed European Bone and Joint Infection Society (EBJIS) criteria. Treatment failure was defined as relapse or persistence of infection. Results. We included 9 patients (4 men and 5 women, mean age 75 years) involving 4 knee and 5 hip joint prosthesis. Risk factors for Candida PJI were prior PJI (n=4), diabetes mellitus (n=3), chronic kidney disease (n=3), obesity (n=3), negative-pressure wound therapy (n=3), rheumatoid arthritis (n=1) and chronic decubitus (n=1). Two patients had no risk factors for Candida PJI identified. Infection was acquired postoperatively (n=7), hematogenously (n=1) or contiguously through communicating vesico-articular sinus (n=1). The causative pathogen was C. albicans in 5, C. parapsilosis in 3, C. tropicalis in 1 patient, isolated from periprosthetic tissue samples (n=7), sonication fluid (n=3) and blood cultures (n=2); bacterial co-pathogens were isolated in 8 patients. Histopathological analysis revealed low-grade inflammation in all 6 patients, in whom it was performed. All patients were treated with oral fluconazole for 3 months, two initially received intravenous caspofungin and three received suppression with oral fluconazole for additional 9 months (total treatment 12 months). Liposomal amphotericin B (300–700 mg per 40 g bone cement) was admixed to spacer cement in 3 patients. Debridement and prosthesis retention was performed in one patient with tumor prosthesis after bone resection due to osteochondrosarcoma. In the remaining 8 patients the prosthesis was removed, with one-stage reimplantation in 1 patient and two-stage reimplantation in 3 patients (after 6 weeks, 3 months and 7 months); two patients are currently awaiting reimplantation, one died due to reason not related to PJI and another underwent knee arthrodesis. Among 5 patients with prosthesis in place, relapse occurred in one patient with prosthesis retention. Another patient experienced new PJI of the exchanged prosthesis caused by Staphylococcus aureus. Conclusions. All Candida PJI presented as chronic infection with low-grade inflammation. Treatment with prostheses retention failed, whereas in 4 patients who underwent two-stage exchange and long-term antifungal suppression, no relapse or persistence of infection was observed. All patients received oral fluconazole for ≥3 months

Aim: A prospective cohort study on the role of flowtron intermittent compression garment (Flowtron) in improving fixed flexion deformity (FFD) in patients coming in for Total Knee Replacement (TKR). Methods: A total of 36 patients with FFD of the knee averaging 26 deg. (range: 22 to 38 deg.) were included. There were 22 men & 14 women, with a mean age of 66 yrs (58 to 78). The diagnosis was osteoarthritis in 26 knees and rheumatoid arthritis in 10. The right knee was involved in 24 patients and the left in 12.There were 26 varus knees and 10 valgus. Patients with peripheral vascular disease and congestive cardiac failure were excluded from the study. Results: Use of flowtrons for one week at home resulted in 80% mean improvement in fixed flexion deformity from an average 26 to 6 degrees (p< 0.001). The residual correction was obtained on the table without excessive posterior release or bone resection. The correction was found to be maintained at 6 months and 1year follow-up. There were no complications with Flowtron treatment. We also noticed that the improvement was better in Osteoarthritis group (26 to 5 degrees) as compared to Rheumatoid arthritis (31 to 9 degrees). Conclusions: Conventional TKR in patients with moderate to severe FFD requires extensive posterior soft tissue release and bone resection. This prolongs surgical time, increases blood loss and has potential soft tissue complications. Flowtron has been used in the past to improve FFD with good early correction but the deformity gradually recurred. We have overcome this problem by doing definitive surgical procedure in the form of TKR. In summary, flowtron is safe and effective in reducing FFD, helping the surgeon to perform TKR without extensive posterior soft tissue release or bone resection with its attendant complications. The correction is maintained with no complications with its use. We recommend that flowtron be used in patients with moderate to severe FFD

Introduction. Variation in resection thickness of the femur in Total Knee Arthroplasty (TKA) impacts the flexion and extension tightness of the knee. Less well investigated is how variation in patient anatomy drives flexion or extension tightness pre- and post- operatively. Extension and flexion stability of the post TKA knee is a function of the tension in the ligaments which is proportional to the strain. This study sought to investigate how femoral ligament offset relates to post-operative navigation kinematics and how outcomes are affected by component position in relation to ligament attachment sites. Method. A database of TKA patients operated on by two surgeons from 1-Jan-2014 who had a pre-operative CT scan were assessed. Bone density of the CT scan was used to determine the medial and lateral collateral attachments. Navigation (OmniNav, Raynham, MA) was used in all surgeries, laxity data from the navigation unit was paired to the CT scan. 12-month postoperative Knee Osteoarthritis and Outcome Score (KOOS) score and a postoperative CT scan were taken. Preoperative segmented bones and implants were registered to the postoperative scan to determine change in anatomy. Epicondylar offsets from the distal and posterior condyles (of the native knee and implanted components), resections, maximal flexion and extension of the knee and coronal plane laxity were assessed. Relationships between these measurements were determined. Surgical technique was a mix of mechanical gap balancing and kinematically aligned knees using Omni (Raynham, MA) Apex implants. Results. 119 patients were identified in the database. 60% (71) were female and the average age was 69.0 years (+/− 8.1). The average distal femoral bone resection was 7.5 mm (+/− 1.6) medially and 5.4 mm (+/− 2.1) laterally, and posterior 10.2 mm (+/− 1.7) medially and 8.4 mm (+/− 1.8) laterally, with implant replacement thicknesses 9 mm distally and 11 mm posterior. Maximum flexion of the knee post implantation was 121.5° (+/− 8.1) from a preoperative value of 117.9° (+/− 9.5). Change in the collateral ligament offsets brought on by surgery had significant correlations with several laxity and flexion measures. Increase in the posterior offset of the medial collateral attachment brought on by surgery was shown to decrease the maximum flexion attained (coefficient = −0.53, p < 0.001), Figure 1. Increased distal medial offset post-operatively compared to the posterior offset is significantly correlated with improved KOOS pain outcomes (coefficient = 0.23, p = 0.01). Similarly, a decrease in the distal offset of the lateral collateral ligament increased the coronal plane laxity in extension (coefficient = 0.37, p < 0.001), while the posterior lateral resection was observed to correlate with postoperative coronal laxity in flexion (coefficient = 0.42, p < 0.001). Conclusions. Accounting for variation in ligament offset during surgically planning may improve balancing outcomes. Although new alignment approaches, such as kinematic alignment, have been able to demonstrate improvements in short term outcomes, elimination of postoperative dissatisfaction has not been achieved. The interaction of an alignment strategy with a given patient's specific anatomy may be the key to unlocking further TKA patient outcome gains

Aims

It is unknown whether gap laxities measured in robotic arm-assisted total knee arthroplasty (TKA) correlate to load sensor measurements. The aim of this study was to determine whether symmetry of the maximum medial and lateral gaps in extension and flexion was predictive of knee balance in extension and flexion respectively using different maximum thresholds of intercompartmental load difference (ICLD) to define balance.

Introduction. Arthritic knees requiring total knee replacement may present with additional deformities located along the femur or tibia away from the articular region. These deformities may be congenital, developmental, associated with metabolic bone disease, or acquired as a result of malunited fractures or previous advocated for arthritic knee with ipsilateral extra-articular deformity. Methods. We undertook retrospective study to evaluate the results of total knee arthroplasty in arthritic knee with extra-articular deformity in 26 knees (24 patients). Sixteen deformities were in tibia and ten deformities were in femur. All patients underwent total knee arthroplasty with intraarticular bone resection and soft tissue balancing. Results. Average period of follow up was 30 months. Average preoperative arc of motion was 57.5 degrees, which improved to 102.5 degrees. The average preoperative knee society knee score 23.5 points, which improved to an average of 91.3 points at the time of last follow up. The average functional score was 27.0 points, which improved to average of 88.0 points. There were no complications such as infection, ligament instability or component loosening. Conclusion. Intra-articular bone resection is an effective procedure for management of arthritic knees with extra-articular deformity

To close the surgeon in the control loop is able to take advantages of the fertile sensing information and intelligence from human being so that the complex and unpredictable surgical procedure can be better handled properly. However, there is also weakness to be strengthened. For example, the motion control of the human being is not as accurate as required. Assisted equipment for such purpose may be helpful to the procedure. Exerting large forces during the cutting process may exhaust the operator and cause fatigue. The operator may need power assistance during the surgery procedure. The response speed of human being's may not be adequate to take immediate action in certain critical situations. The constraints from the limbs and human's attention usually cause a significant delay to react the critical situations. This may lead to serious damage by failing to response immediately. For example, in knee replacement procedure, the shape of the knee joint has to be prepared by performing bone resection procedure. The surgeon cuts the bone at certain position and orientation with the help of the cutting jig from the surgical planning. The cutter cut the bone by inserting vibration saw through the slot of the cutting block. The surgeon has to stop the cutter right after the bone has been cut through by the saw so that no surrounding soft tissue, blood vessel, and even important nerves, be damaged. Currently the tactile sensing from the hand is heavily relied on by the surgeon. He has also to be experienced and dexterous. If he fails to draw back the cutter after the bone being cut through, damages to the patient may occur. Therefore there is need to develop a cutting tool, which is intelligent, knows where it is, and is able to judge what the cutting situation is, and further assists the operator to stop the cutter in case that the operator fails to do so, or too slow to response. The benefit to the patient as well as the surgeon will be significant. Therefore the purpose of the paper is to develop an algorithm to implement such functionality of auto-detection of bone cutting through for a bone cutting tool when the cutter has cut through the bone. By the developed method, the intelligent cutter can effectively detect the cutting through condition and then adopt an immediate reaction to prevent the cutter from going further and to avoid unexpected damage. An auto-detection scheme has also been developed for assisting the operator in judging whether the cutter has reached the boundary or not. The auto-detection scheme is based on analyzing the cutting force pattern in conjunction with a bilateral force controller for the hand's on robot. The bilateral force controller consists of two force controllers. The force controller on the master calculates the feedrate of the cutter according to the push force by the operator. Meanwhile, the operator can also feel the cutting force by the force controller on the slave site, which revises the feedrate of the cutter by the measured cutting force. The operator can kinesthetically feel the cutting force from the variation of the feedrate. When the cutter breaks through the boundary of the bone, the cutting force will drop suddenly to almost zero. When this special force pattern occurs, an acknowledge signal of bone been broken through will be activated. The subsequent action will be followed to stop the cutter going further. We implement this concept by defining a “cutting admittance” indicating the resistance encountered by the cutting during bone resection at different cutting feedrate. During the bone resection, the cutting admittance varies from cutting through hard or soft portions of bone. As reaching the cutting boundary, the cutting admittance will suddenly increase. A threshold value will experimentally be determined to indicate cutting through condition. Together with pushing force by the human operator, the criterion for cutting-through detection is defined. Once cutting through is detected, the admittance for cutter movement will be set zero. The cutter stops going further and the operator feel like hitting a virtual wall in front. In this paper we proposed a human robot cooperative operation method by which the robotic system can intelligently detect where the cutter has cut through the bone. Characterisation of bone cutting procedure was performed. This auto detection scheme was developed by analyzing the information of the motion and cutting force information during the bone cutting process, no medical images are required. The auto-detection bone cut through was able to transfer the experiences of human being to quantitative modeling. The developed model has been tested for its applicability and robustness by saw bones and pig's knee joints. Results have shown the virtual wall generated by the real-time bone detection scheme and active constraint control is very accurate and capable of providing a safety enhance module for computer assisted orthopaedic surgery, in particular, in total knee replacement. By this method the robot system can accomplish a safe and accurate bone cutting with a complement of an imageless navigation system and results in a low cost, but safe and effective surgical robot system