Aims. The aim of this study was to evaluate medium- to long-term outcomes and complications of the Stanmore Modular Individualised Lower Extremity System (SMILES) rotating hinge implant in revision total knee arthroplasty (rTKA) at a tertiary unit. It is hypothesized that this fully cemented construct leads to satisfactory clinical outcomes. Methods. A retrospective consecutive study of all patients who underwent a rTKA using the fully cemented SMILES rotating hinge prosthesis between 2005 to 2018. Outcome measures included aseptic loosening, reoperations, revision for any cause, complications, and survivorship. Patients and implant survivorship data were identified through both prospectively collected local hospital electronic databases and linked data from the National Joint Registry/NHS Personal Demographic Service. Kaplan-Meier survival analysis was used at ten years. Results. Overall, 69 consecutive patients (69 knees) were included with a median age of 78 years (interquartile range 69 to 84), and there were 46 females (66.7%). Indications were septic revisions in 26 (37.7%), and aseptic aetiology in the remining 43 (62.3%). The mean follow-up was 9.7 years (4 to 18), and the overall complication was rate was 7.24%, all with patellofemoral complications. Failure rate with ‘any cause revision’ was 5.8%. There was one case of aseptic loosening of the femoral component. At ten years, 17/69 patients (24.63%) had died, and implant survivorship was 92.2%. Conclusion. In our experience, the SMILES rotating hinge prosthesis achieves satisfactory long-term outcomes with ten-year implant survivorship of 92.2% and a patellofemoral complication rate of 7.24%. Cite this article: Bone Jt Open 2023;4(10):776–781

Aims

The aim of this study was to evaluate medium-term outcomes and complications of the S-ROM NOILES Rotating Hinge Knee System (DePuy, USA) in revision total knee arthroplasty (rTKA) at a tertiary unit.

Background. One of the major concerns of hinge knees have been reported in literature is mechanical failure. Failure in the form of component fracture (2–10%) and hinge dislocation/ failure are worrisome. In addition, higher risk of aseptic loosening with hinge knee prosthesis has been attributed to stress transfer at bone cement interface. Methods. Retrospective review of clinical and radiological results of 71 consecutive patients operated at single centre using Smiles hinge knee (Stanmore implants) between 2010 and 2014. Data was collected till the latest follow up. Mechanical failure due to any reason was considered as primary end point. Radiological evidence of aseptic loosening was considered to be one of the surrogate end points. Results. Mean age at revision knee was 65.4 years (range 42 – 84). The number of previous revisions ranged from 1 – 4. Most common indications for revision were infection (n=26) and instability (n=26). Majority of patients had rotating hinge knee (n=66). Average follow-up was 31 months (range 3 – 72). Four patients died during follow-up due to medical reasons. There were no mechanical failures of implants apart from backing out of axle due to failure of circlip in 1 patient. Asymptomatic aseptic loosening of implant on femoral side was noted in 1 patient; however, there were no peri-prosthetic fractures in this series. Three patients had re-revision for infection and one for extensor mechanism subluxation. Conclusion. To our knowledge, this is the largest series till date reporting on mechanical outcomes of hinged knee implants for complex revisions. Clip failure is of concern; however there have been no other mechanical failures. Early results are encouraging, with no symptomatic aseptic loosening of implants to report

The aim of this study was to analyse the gait pattern, muscle force and functional outcome of patients who had undergone replacement of the proximal tibia for tumour and alloplastic reconstruction of the extensor mechanism using the patellar-loop technique.

Between February 1998 and December 2009, we carried out wide local excision of a primary sarcoma of the proximal tibia, proximal tibial replacement and reconstruction of the extensor mechanism using the patellar-loop technique in 18 patients. Of these, nine were available for evaluation after a mean of 11.6 years (0.5 to 21.6). The strength of the knee extensors was measured using an Isobex machine and gait analysis was undertaken in our gait assessment laboratory. Functional outcome was assessed using the American Knee Society (AKS) and Musculoskeletal Tumor Society (MSTS) scores.

The gait pattern of the patients differed in ground contact time, flexion heel strike, maximal flexion loading response and total sagittal plane excursion. The mean maximum active flexion was 91° (30° to 110°). The overall mean extensor lag was 1° (0° to 5°). The mean extensor muscle strength was 25.8% (8.3% to 90.3%) of that in the non-operated leg (p < 0.001). The mean functional scores were 68.7% (43.4% to 83.3%) (MSTS) and 71.1 (30 to 90) (AKS functional score).

In summary, the results show that reconstruction of the extensor mechanism using this technique gives good biomechanical and functional results. The patients’ gait pattern is close to normal, except for a somewhat stiff knee gait pattern. The strength of the extensor mechanism is reduced, but sufficient for walking.

Cite this article: Bone Joint J 2015;97-B:1063–9.

Patients with skeletal dysplasia are prone to developing advanced degenerative knee disease requiring total knee replacement (TKR) at a younger age than the general population. TKR in this unique group of patients is a technically demanding procedure due to the bone deformity, flexion contracture, generalised hypotonia and ligamentous laxity. We set out to retrospectively review the outcome of 11 TKR's performed in eight patients with skeletal dysplasia at our institution using the SMILES custom-made rotating-hinge total knee system. There were 3 males and 5 females with mean age 57 years (range, 41–79 years), mean height 138 cm (range, 122–155 cm) and mean weight 56 kg (range, 40–102 kg). Preoperative diagnoses included achondroplasia, spondyloepiphyseal dysplasia, pseudoachondroplasia, multiple epiphyseal dysplasia, morquio syndrome, diastrophic dysplasia and Larson's Syndrome. Patients were followed clinically and radiographically for a mean of 7 years (range, 3–11.5 years). Knee pain and function improved in all 11 joints. Mean Knee Society clinical and function scores improved from 24 (range, 14–36) and 20 points (range, 5–40) preoperatively to 68 (range, 28–80) and 50 points (range, 22–74) respectively at final follow-up. Four complications were recorded (36%), including a patellar fracture following a fall, a tibial periprosthetic fracture, persistent anterior knee pain and a femoral component revision for aseptic loosening. Our results suggest that custom rotating-hinge TKR in patients with skeletal dysplasia is effective at relieving pain, optimising movement and improving function. It compensates for bony deformity and ligament deficiency and reduces the need for corrective osteotomy. Patellofemoral joint complications are frequent and functional outcome is worse than primary TKR in the general population. Submission endorsed by Mr Peter Calder, Consultant Orthopaedic Surgeon and Society member

Polymethyl methacrylate spacers are commonly used during staged revision knee arthroplasty for infection. In cases with extensive bone loss and ligament instability, such spacers may not preserve limb length, joint stability and motion. We report a retrospective case series of 19 consecutive patients using a custom-made cobalt chrome hinged spacer with antibiotic-loaded cement. The “SMILES spacer” was used at first-stage revision knee arthroplasty for chronic infection associated with a significant bone loss due to failed revision total knee replacement in 11 patients (58%), tumour endoprosthesis in four patients (21%), primary knee replacement in two patients (11%) and infected metalwork following fracture or osteotomy in a further two patients (11%). Mean follow-up was 38 months (range 24–70). In 12 (63%) patients, infection was eradicated, three patients (16%) had persistent infection and four (21%) developed further infection after initially successful second-stage surgery. Above knee amputation for persistent infection was performed in two patients. In this particularly difficult to treat population, the SMILES spacer two-stage technique has demonstrated encouraging results and presents an attractive alternative to arthrodesis or amputation

Introduction. We discuss the use of the SMILES (Stanmore Modular Individualised Lower Extremity System) in salvage revision knee surgery and review the medium-long term results of 42 cases. Methods. This is a prospective, single-centre study. The SMILES prosthesis is a custom-made implant incorporating a rotating hinge knee joint. 42 prostheses were used in 40 patients as salvage revision procedures between September 1991 and September 1999. Patients undergoing surgery for tumours were excluded. The minimum follow-up was seven years with a mean follow-up of ten years and six months. Patients were independently assessed using the Knee Society Rating Score. The age of the patients ranged from 36-85 years (mean 68 years and 6 months). 23 of the patients were male. The original pathology was osteoarthritis in 32 patients and rheumatoid arthritis in 8 patients. The number of previous arthroplasties ranged from 1-4. The main indications for a SMILES prosthesis were aseptic loosening, periprosthetic fracture and infection in the presence of bone loss and ligamentous laxity. Results. There was a highly statistically significant improvement in overall Knee Society scores from a mean of 26 pre-op to 72 post-op. The mean knee score improved from 26 pre-op to 68 post-op while the mean function score improved from 27 to 75. The average range of motion was 60 degrees pre-op and 90 degrees post-op. Complications included: failure to eradicate infection in two patients, with one patient needing amputation; infection of the prosthesis leading to revision in one, and failure of the tibial component needing revision. Conclusion. The SMILES has produced satisfactory results in the medium to long term, offering an alternative to amputation in some cases. The cost compares favourably with other designs and the use is increasing in frequency

In skeletally immature patients, resection of bone tumours and reconstruction of the lower limb often results in leg-length discrepancy. The Stanmore non-invasive extendible endoprosthesis, which uses electromagnetic induction, allows post-operative lengthening without anaesthesia. Between 2002 and 2009, 55 children with a mean age of 11.4 years (5 to 16) underwent reconstruction with this prosthesis; ten patients (18.2%) died of disseminated disease and one child underwent amputation due to infection. We reviewed 44 patients after a mean follow-up of 41.2 months (22 to 104). The mean Musculoskeletal Tumor Society score was 24.7 (8 to 30) and the Toronto Extremity Salvage score was 92.3% (55.2% to 99.0%). There was no local recurrence of tumour. Complications developed in 16 patients (29.1%) and ten (18.2%) underwent revision.

The mean length gained per patient was 38.6 mm (3.5 to 161.5), requiring a mean of 11.3 extensions (1 to 40), and ten component exchanges were performed in nine patients (16.4%) after attaining the maximum lengthening capacity of the implant. There were 11 patients (20%) who were skeletally mature at follow-up, ten of whom had equal leg lengths and nine had a full range of movement of the hip and knee.

This is the largest reported series using non-invasive extendible endoprostheses after excision of primary bone tumours in skeletally immature patients. The technique produces a good functional outcome, with prevention of limb-length discrepancy at skeletal maturity.

Patients with skeletal dysplasia are prone to developing advanced osteoarthritis of the knee requiring total knee replacement (TKR) at a younger age than the general population. TKR in this unique group of patients is a technically demanding procedure owing to the deformity, flexion contracture, generalised hypotonia and ligamentous laxity. We retrospectively reviewed the outcome of 11 TKRs performed in eight patients with skeletal dysplasia at our institution using the Stanmore Modular Individualised Lower Extremity System (SMILES) custom-made rotating-hinge TKR. There were three men and five women with mean age of 57 years (41 to 79). Patients were followed clinically and radiologically for a mean of seven years (3 to 11.5). The mean Knee Society clinical and function scores improved from 24 (14 to 36) and 20 (5 to 40) pre-operatively, respectively, to 68 (28 to 80) and 50 (22 to 74), respectively, at final follow-up. Four complications were recorded, including a patellar fracture following a fall, a tibial peri-prosthetic fracture, persistent anterior knee pain, and aseptic loosening of a femoral component requiring revision. Our results demonstrate that custom primary rotating-hinge TKR in patients with skeletal dysplasia is effective at relieving pain, with a satisfactory range of movement and improved function. It compensates for bony deformity and ligament deficiency and reduces the likelihood of corrective osteotomy. Patellofemoral joint complications are frequent and functional outcome is worse than with primary TKR in the general population.

We undertook a retrospective review of 33 patients who underwent total femoral endoprosthetic replacement as limb salvage following excision of a malignant bone tumour. In 22 patients this was performed as a primary procedure following total femoral resection for malignant disease. Revision to a total femoral replacement was required in 11 patients following failed segmental endoprosthetic or allograft reconstruction. There were 33 patients with primary malignant tumours, and three had metastatic lesions. The mean age of the patients was 31 years (5 to 68). The mean follow-up was 4.2 years (9 months to 16.4 years). At five years the survival of the implants was 100%, with removal as the endpoint and 56% where the endpoint was another surgical intervention. At five years the patient survival was 32%. Complications included dislocation of the hip in six patients (18%), local recurrence in three (9%), peri-prosthetic fracture in two and infection in one. One patient subsequently developed pulmonary metastases. There were no cases of aseptic loosening or amputation. Four patients required a change of bushings. The mean Musculoskeletal Tumour Society functional outcome score was 67%, the mean Harris Hip Score was 70, and the mean Oxford Knee Score was 34.

Total femoral endoprosthetic replacement can provide good functional outcome without compromising patient survival, and in selected cases provides an effective alternative to amputation.

Introduction: We report our experience with use of the SMILES prosthesis in primary knee arthroplasty. Methods: The Stanmore Modular Individualised Lower Extremity System (SMILES prosthesis) has been shown to be effective in complex revision knee surgery. It incorporates a rotating hinge platform knee joint and can overcome the major problems of bone loss and ligamentous laxity. 38 patients (41 knees) who received a primary SMILES knee prosthesis by one of the senior authors between 1990 and 2006 were retrospectively studied. Knee function was assessed pre and post-operatively using the Oxford knee score (0–48 scoring system) and the Knee Society Score. Patients receiving surgery for tumours were excluded. The main indications for primary SMILES were bone loss and ligamentous laxity. Results: The minimum follow-up was 18 months with a mean of 5 years (1–17). The mean age of the patients was 57.7 years (23–86); 15 of the patients were male. The indications for surgery were trauma (12), osteoarthritis with deficient medial collateral ligament (8), polio (7), rheumatoid arthritis (5), epiphyseal dysplasia (4), achondroplasia (2), avascular necrosis (1), osteogenesis imperfecta (1) and ankylosing spondylitis (1). 2 patients died and 5 were lost to follow-up. 2 patients required revision surgery (one for infection and one for re-bushing). Post-operative complications included peroneal nerve palsy (1) and DVT (1). The mean Oxford knee score improved from 9 pre-op to 44 post-op, and the mean knee society score improved from 24 pre-op to 71 post-op. The average range of motion was 57 degrees pre-op and 88 degrees post-op. Conclusion: We conclude that the SMILES prosthesis offers significant improvement in clinician and patient assessed outcome scores in complex primary knee arthroplasty. The cost compares favourably with other designs and its use is well established

The purpose of this study was to determine whether the low rate of mechanical loosening of the SMILES rotating hinge distal femoral endoprosthesis relates to the hydroxyapatite (HA)-coated, grooved collar of the femoral component. A database was used to identify two groups of cases of primary distal femoral replacement with a custom-designed and manufactured SMILES endoprosthesis at our unit; those with the collared femoral component (“collar group”), and those without a collar (“non-collargroup”). From these two groups, patients were pair-matched for age and length of bone resection. A retrospective review of serial biplanar pairs of radiographs of each patient, assessing radiolucent lines and extracortical bone pedicle. 11 matched pairs were identified, (14 females, 8 males), with a mean age of 36 years, (range 16–66). The pathology was primary bone tumour in 20 cases, (17 malignant, 3 benign), and metastatic disease in 2 cases. Mean length of follow-up was 85 months, (range 27–122). Radiolucent line score (RLS) progression over time was significantly lower in the collar group, (0.01 vs 0.73, p=0.001) (fig. 1 & 2), as was the mean final RLS, (2.72 vs 7.81, p=0.02). Mean RLS per radiographic quadrant was 0.56 in cases in which a bony pedicle was ingrown onto the prosthesis, (exclusively in the collared-group), 2.41 in cases in which the pedicle was not ingrown, (most prevalent in the non-collared group), and 1.02 in those cases without any pedicle formation, (ANOVA analysis, p=0.0002). This study demonstrates that the HA-coated, grooved collar significantly reduces the progression of radiolucent lines, and consequently the overall RLS, explaining the reduced rate of mechanical loosening of the collared endoprosthesis. A bony pedicle that does not incorporate onto the prosthesis surface may be associated with an increase in radiographic loosening

Introduction: Total femoral endoprosthetic replacement can be an alternative to amputation following extensive tumour excision or in cases of severe bone loss. In skeletally immature patients the problem of leg length inequality may be overcome by the use of extendable prostheses. The aim of this study is to assess the functional outcome of patients following total femoral endoprosthetic replacement. Methods: This is a retrospective, single centre study of 16 patients who underwent consecutive total femoral replacements between 1978 and 1999. Information was collected from the Bone Tumour database, medical records and clinical review. The prostheses were custom made by the Biomedical Engineering Department of University College London and Stanmore Implants Worldwide. The implants are composed of a Titanium alloy shaft with Cobalt-Chrome bearing surfaces, incorporating a SMILES (Stanmore Modular Individualised Lower Extremity System) knee joint. Outcome was assessed using the Musculoskeletal Tumour Society (MTS) rating score. Sample: Eight patients were male and eight female. Mean age was 35 years (range 5–75 years). Ten patients underwent total femoral replacement as a primary procedure; nine for malignant tumour and one for hydatid disease. Of the patients with malignancy five had metastases at the time of presentation. The other indications were failed distal femoral replacement in four cases and periprosthetic fractures in the remaining two. Four children received extendable prostheses. Results: Of the patients with malignant disease, all but one had complete tumour excision. Three patients developed local recurrence. Two patients died of metastases within one year of diagnosis and three more died within five years. Three required revision procedures. Two more dislocated at the hip joint. Other complications included infection and lymphoedema. In patients surviving longer than one year the average range of motion at the hip was 85 degrees and at the knee 80 degrees. Using the MTS rating score the mean functional outcome was 60% of normal (range 27–90%). Of the survivors one achieved an excellent result, five were good, four fair and one poor. Conclusion: Total femoral endoprosthetic replacement can be effective in limb salvage and provide an alternative to amputation. Good functional results can often be achieved. However, the complication rate is high and the outcome extremely varied

Purpose: The purpose of this study was to determine whether the low rate of mechanical loosening of the SMILES rotating hinge distal femoral endoprosthesis relates to the hydroxyapatite (HA)-coated, grooved collar of the femoral component. Methods and results: A database was used to identify two groups of cases of primary distal femoral replacement with a custom-designed and manufactured SMILES endoprosthesis at our unit; those with the collared femoral component (“collar group”), and those without a collar (“non-collar group”). From these two groups, patients were pair-matched for age and length of bone resection. We performed a retrospective review of serial biplanar pairs of radiographs of each patient, assessing radiolucent lines and extracortical bone pedicle. 11 matched pairs were identified, (14 females, 8 males), with a mean age of 36 years, (range 16–66). The pathology was primary bone tumour in 20 cases, (17 malignant, 3 benign), and metastatic disease in 2 cases. Mean length of follow-up was 85 months, (range 27–122). Radiolucent line score (RLS) progression over time was significantly lower in the collar group, (0.01 vs 0.73, p=0.001) (fig. 1 & 2), as was the mean final RLS, (2.72 vs 7.81, p=0.02). Mean RLS per radiographic quadrant was 0.56 in cases in which a bony pedicle was ingrown onto the prosthesis, (exclusively in the collared-group), 2.41 in cases in which the pedicle was not ingrown, (most prevalent in the non-collared group), and 1.02 in those cases without any pedicle formation, (ANOVA analysis, p=0.0002). Conclusion: This study demonstrates that the HA-coated, grooved collar significantly reduces the progression of radiolucent lines, and consequently the overall RLS, explaining the reduced rate of mechanical loosening of the SMILES prosthesis. A bony pedicle that does not incorporate onto the prosthesis surface may be associated with an increase in radiographic loosening

It is well recognized that following excision of bone tumours around the knee, which often requires excision of the joint, cemented fixed hinged endoprosthetic replacements can give excellent results in terms of function (87%). However, for patients under 20 years of age the overall survivorship of distal femoral replacements in this age group is less than 45% at 10 years. To try and address this we have used HA ingrowth collars since 1989 and introduced the Smiles rotating hinge in 1991. In the younger patients we have also used uncemented prostheses using HA. The HA collars at 70mm thickness are now standard protocol on all extremeity endoprosthetic replacements. We will present the results of retrieval specimens. We have also undertaken a study to determine the effect that HA collars and roating hinges have on enhancement of implant fixation. A survivorship and radiographic analysis has been carried out with three groups of patients: 1. Fixed hinge no collar. 2. Rotating hinge no collar. 3. Rotating hinge with HA collar. The selection criteria were all distal femoral replacements of patients who were over 16 years of age and had a cemented intramedullary stem. The study groups were consistent for age and amount of bone resected and all patients have been followed up

Then SMILES (Stanmore Modular International Limb Salvage System) was first introduced in 1991 for use as a customized prosthesis in the treatment of malignant and aggressive bone tumours. However, the use of this pros-thesis has been extended to minimal customization, to be used in a situation of salvage surgery for the arthrosplasty, which has already undergone previous revision surgery. Between 1991 and 1997 32 SMILES prostheses were used in thismanner in 30 patients. 28 patients were available for review, all had a minimum of 3 years follow-up. The mean number of previous revision procedures was 2 and 6, average 2.6. There were 11 male and 19 female patients. The mean age at the time of the salvage procedure was 67 years (46 to 86). The mean age of the primary procedure was 57.8 (Range 43–71). The Knee Society score increased from 26 to 68 and the function score increase from 26 and 68 and the function score increased from 27 to 75. Average flexion improved post-operatively from 78 to 88 degrees. 84% of patients stated that they were pleased with the results in terms of pain and mobility. We conclude that this prosthesis is a satisfactory alternative to complex reconstructions or amputation in the presence of infection, severe bone or soft tissue loss and has rendered acceptable results

Introduction: We discuss the use of the SMILES (Stanmore Modular Individualised Lower Extremity System) in revision knee arthroplasty and review the outcome of 32 cases. Methods: The SMILES prosthesis incorporates a rotating hinge knee joint. It can overcome the major problems of bone loss and ligamentous laxity. 32 prostheses were used in 30 patients as salvage revision procedures between Sept. 1991 and Sept. 1998. Patients receiving surgery for tumours were excluded. The minimum follow-up was two years with a mean follow-up of 4 years and six months. The age of the patients ranged from 36–85 years (mean 68years and 6months). 18 of the patients were male. The original pathology was OA in 23 patients and RA in 7 patients. The number of previous arthroplasties ranged from 1–4. The main indications for a SMILES prosthesis were aseptic loosening, periprosthetic fracture and infection, in the presence of bone loss and ligamentous laxity. Results: The patients were assessed using the Knee Society Rating Score. The mean knee score improved from 26 pre-op to 68 post-op while the mean fiction score improved from 27 to 75. Overall Knee Society scores improved from a mean of 26 to 72. The average range of motion was 60 degrees pre-op and 90 degrees post-op. Complications included: failure to eradicate infection in two patients, with one patient needing amputation; infection of the prosthesis leading to revision in one, and failure of the tibial component needing revision. Conclusion: The Smiles has produced satisfactory results in the short to medium term, offering an alternative to amputation in some cases. The cost compares favourably with other designs and the use is increasing in frequency