Objectives. A successful outcome following treatment of nonunion requires the correct identification of all of the underlying cause(s) and addressing them appropriately. The aim of this study was to assess the distribution and frequency of causative factors in a consecutive cohort of nonunion patients in order to optimise the management strategy for individual patients presenting with nonunion. Methods. Causes of the nonunion were divided into four categories: mechanical; infection; dead bone with a gap; and host. Prospective and retrospective data of 100 consecutive patients who had undergone surgery for long bone fracture nonunion were analysed. Results. A total of 31% of patients had a single attributable cause, 55% had two causes, 14% had three causes and 1% had all four. Of those (31%) with only a single attributable cause, half were due to a mechanical factor and a quarter had dead bone with a gap. Mechanical causation was found in 59% of all patients, dead bone and a gap was present in 47%, host factors in 43% and infection was a causative factor in 38% of patients. In all, three of 58 patients (5%) thought to be aseptic and two of nine (22%) suspected of possible infection were found to be infected. A total of 100% of previously treated patients no longer considered to have ongoing infection, had multiple positive microbiology results. Conclusion. Two thirds of patients had multiple contributing factors for their nonunion and 5% had entirely unexpected infection. This study highlights the importance of identifying all of the aetiological factors and routinely testing tissue for infection in treating nonunion. It raises key points regarding the inadequacy of a purely radiographic nonunion classification system and the variety of different definitions for atrophic nonunion in the current mainstream classifications used for nonunion. Cite this article: L. Mills, J. Tsang, G. Hopper, G. Keenan, A. H. R. W. Simpson. The multifactorial aetiology of fracture nonunion and the importance of searching for latent infection. Bone Joint Res 2016;5:512–519. DOI: 10.1302/2046-3758.510.BJR-2016-0138

Dual mobility significantly reduces the risk of prosthetic instability. This mechanical complication occurs when the prosthetic head moves out from the retentive polyethylene liner, such phenomenon called intra-prosthetic dislocation reports a ten-year incidence of 2% in the literature.

We prospectively analysed all intra-prosthetic dislocations having occurred since 1985 in our department in order to investigate patient- and implant-related risk factors.

91 intra-prosthetic dislocations occurred with NOVAE (SERF) cups in 85 patients of mean age 50.7 years. Intra-prosthetic dislocation occurred after a mean period of 8.8 years.

A PRO (SERF) stem was implanted in 56 cases and a PF (SERF) stem in 35. The stems were different from one another in their neck diameter and material: 13 mm titanium neck and 16 mm stainless steel neck respectively.

When taking both prosthetic features into account, no significant difference could be established regarding the time between implantation and dislocation.

Comparison between these two prosthetic features was performed by means of two continuous homogeneous series which included 240 patients implanted with PF stems and 382 patients with PRO stems. At a mean 15-year follow-up, the two series reported a non-statistically different intra-prosthetic dislocation rate of 4%.

In both series, young age and large diameter cups were considered predisposing factors for intra-prosthetic dislocation.

Therefore, unlike suggested by several authors, prosthetic neck material and diameter do not appear as the main predictors for intra-prosthetic dislocation which is highly promoted by patient-related features.

Aims. This study aimed to investigate the clinical characteristics and outcomes associated with culture-negative limb osteomyelitis patients. Methods. A total of 1,047 limb osteomyelitis patients aged 18 years or older who underwent debridement and intraoperative culture at our clinic centre from 1 January 2011 to 31 December 2020 were included. Patient characteristics, infection eradication, and complications were analyzed between culture-negative and culture-positive cohorts. Results. Of these patients, 264 (25.2%) had negative cultures. Patients with a culture-negative compared with a culture-positive status were more likely to have the following characteristics: younger age (≤ 40 years) (113/264 (42.8%) vs 257/783 (32.8%); p = 0.004), a haematogenous aetiology (75/264 (28.4%) vs 150/783 (19.2%); p = 0.002), Cierny-Mader host A (79/264 (29.9%) vs 142/783 (18.1%); p < 0.001), antibiotic use before sampling (34/264 (12.9%) vs 41/783 (5.2%); p＜0.001), fewer taken samples (n＜3) (48/264 (18.2%) vs 60/783 (7.7%); p＜0.001), and less frequent presentation with a sinus (156/264 (59.1%) vs 665/783 (84.9%); p < 0.001). After initial treatments of first-debridement and antimicrobial, infection eradication was inferior in culture-positive osteomyelitis patients, with a 2.24-fold increase (odds ratio 2.24 (95% confidence interval 1.42 to 3.52)) in the redebridement rate following multivariate analysis. No statistically significant differences were found in long-term recurrence and complications within the two-year follow-up. Conclusion. We identified several factors being associated with the culture-negative result in osteomyelitis patients. In addition, the data also indicate that culture negativity is a positive prognostic factor in early infection eradication. These results constitute the basis of optimizing clinical management and patient consultations. Cite this article: Bone Joint J 2024;106-B(7):720–727

Deficiency in the gluteus medius and minimus abductor muscles is a well-recognised cause of hip pain and considerable disability. These patients present a management challenge, with no established consensus for surgical intervention. Whiteside in 2012 described a surgical technique for gluteus maximus tendon transfer, with successful outcomes reported. This study is the largest known case series to date of patients undergoing gluteus maximus tendon transfer with clinical and patient reported outcomes measured. 13 consecutive patients were included in the study. All patients had clinical evidence of abductor dysfunction together with MRI evidence of gluteal atrophy and fat infiltration. All patients underwent gluteus maximus transfer with surgery performed according to the procedure described by Whiteside. Patients were followed up with both clinical assessment and patient questionnaires conducted. Mean age was 69 (range 54–82) with 9 patients (69%) having previous Hardinge approach to the affected hip. 6 patients (46%) reported they were satisfied overall with the procedure and 5 patients (38%) were unsatisfied. 7 patients (54%) had improvements in visual analogue scale of pain and 5 patients (54%) reported overall improvements in function. Mean Oxford Hip Score on follow up was 20/48 (range 5–48) and trendelenberg test was positive in 11 patients (85%). No differentiating variable could be identified between patients with positive and negative outcomes (Assessed Variables: Age, sex, BMI, aetiology and gluteus maximus muscle thickness). Clinical outcomes were varied following gluteus maximus tendon transfer for chronic hip abductor dysfunction. Results are considerably less promising than pre-existing studies would suggest

Aims

The aim of the present study was to assess the outcomes of the induced membrane technique (IMT) for the management of infected segmental bone defects, and to analyze predictive factors associated with unfavourable outcomes.

Purpose. to analyze the survivorship of the RSA with a minimum 10 years follow up. Patients and Methods. Between 1992 and 1999, 145 Delta (DePuy) RSAs have been implanted in 138 patients. It was a mulicentric study. Initial etiologies were gathered as following: group A (92 cases) Cuff tear arthropaties (CTA), osteoarthritis (OA) with at least 2 involved cuff tendons, and massive cuff tear with pseudoparalysis (MCT); group B (39 cases) -failed hemiarthroplasties (HA), failed total shoulder arthroplasties (TSA), and fracture sequelae; and group C (14 cases) rheumatoid arthritis, fractures, tumor, and instability. Survival curves were established with the Kaplan-Meier technique. Two end-points were retained: -implant revision, defined by glenoid or humeral replacement or removal, or conversion to HA; - a poor clinical outcome defined by an absolute Constant score of less than 30. Results. At the time of review, 47 patients had died with their prosthesis in place and 30 were lost to follow-up. There were 12 revisions, 6 for infections, 3 for glenoid loosening, 1 for dislocation, 1 for glenoid dissociation (by unscrewing), and 1 for humeral loosening. The survival curve to prosthetic removal showed an overall survivorship of 92% at 10 years. Segmentation according to etiology showed a 97% survivorship for group A and 88% for group B This difference was not significant. No patients of group C had a minimum follow up of ten years because there were died or lost to follow up. The survival curve to a Constant score of less than 30 showed an overall survivorship of 90% at 10 years. Segmentation according to etiology showed a significant difference at 10 years in favor of group A (92%) compared to group B (86%) with a break of the curve after 9 years for group B. Discussion. Our results show that the overall survivorship of the reverse shoulder prosthesis to removal is good even 10 years after implantation, in particular if it had been implanted for CTA, OA, or MCT. However, functional results did deteriorate progressively after 9 years in particular if it had been implanted for revision (HA or TSA). Therefore, extreme caution must be observed in relation to the indications for reverse shoulder arthroplasty, especially in younger patients

Aims

Ankle fracture fixation is commonly performed by junior trainees. Simulation training using cadavers may shorten the learning curve and result in a technically superior surgical performance.

Aims

The aim of this study was to assess whether it is possible to predict the mortality, and the extent and time of neurological recovery from the time of the onset of symptoms and MRI grade, in patients with the cerebral fat embolism syndrome (CFES). This has not previously been investigated.

We explored the role of iron overload, deficiency of vitamin C and alcohol abuse in the aetiology of cervical and intertrochanteric fractures of the neck of the femur as a result of minor trauma. We studied prospectively 72 patients (45 men, 27 women). Levels of serum iron markers, vitamin C and alcohol markers were measured. Consumption of alcohol was estimated using questionnaires. The findings were compared with those of an age- and gender-matched control group. The mean age of the men was 59.5 years and of the women 66.9 years, with a male predominance. In the men, iron overload, as shown by high levels of serum ferritin (p < 0.001) and deficiency of vitamin C (p < 0.03), as well as abuse of both Western and the traditional type of alcohol, appear to be important aetiological factors. In women, alcohol abuse was also common, but iron markers and levels of vitamin C did not differ significantly from the control group

Background:. Leg length discrepancy related to absence of the femoral head with proximal migration of the femur presents a treatment dilemma. Late sequelae of neonatal hip sepsis and chronic hip dislocation due to developmental dysplasia are the most common causes. Traditional teaching dictates that the hip is stabilised prior to limb lengthening. Reconstructive options alter the shape of the proximal femur which complicates future surgery. Methods:. We retrospectively reviewed 3 cases of femoral lengthening with an ‘unstable’ hip without prior stabilization. The aetiology was neonatal hip sepsis in 2 cases and chronic hip dislocation due to developmental dysplasia in 1 case. Lengthening was performed with the use of a retrograde Precice lengthening nail. Results and Discussion:. The desired length (range 5.5 to 6cm) was achieved in all patients without migration of the proximal femur. In all cases patient satisfaction was high with the lengthening and the ability to abort shoe raises. There was an improvement in gait pattern in all patients. Conclusion:. Femoral lengthening is possible without prior stabilisation of the hip in so called ‘unstable’ hip situations. The proximal femoral anatomy is not further altered and future salvage procedures such as a total hip replacement are not compromised

Aims

The study objective was to prospectively assess clinical outcomes for a pilot cohort of tibial shaft fractures treated with a new tibial nailing system that produces controlled axial interfragmentary micromotion. The hypothesis was that axial micromotion enhances fracture healing compared to static interlocking.

The aim of this study was to document our experience of acute forearm compartment syndrome, and to determine the risk factors for requiring split skin grafting (SSG) and developing complications post fasciotomy. We identified from our trauma database all patients who underwent fasciotomy for an acute forearm compartment syndrome over a 22-year period. Diagnosis was made using clinical signs and/or compartment pressure monitoring. Demographic data, aetiology, management, wound closure, complications and subsequent surgeries were recorded. Outcome measures were the use of SSG and the development of complications following forearm fasciotomy. 90 patients were identified with a mean age of 33 yrs (range, 13–81 yrs) and a significant male predominance (n=82, p<0.001). A fracture of one or both of the forearm bones was seen in 62 (69%) patients, with soft tissue injuries causative in 28 (31%). The median time to fasciotomy was 12hrs (2–72). Delayed wound closure was achieved in 38 (42%) patients, with 52 (58%) undergoing SSG. Risk factors for requiring a SSG were younger age and a crush injury (both p<0.05). Complications occurred in 29 (32%) patients at mean follow-up of 11 (3–60) months. Risk factors for developing complications were a delay in fasciotomy of >6 hrs (p=0.018), with pre-operative motor symptoms approaching significance (p=0.068). Forearm compartment syndrome requiring fasciotomy predominantly affects males and can occur following either a fracture or soft tissue injury. Age is an important predictor of undergoing SSG for wound closure. Complications occur in a third of patients and are associated with an increasing delay in the time to fasciotomy

Introduction. Anterior knee pain is a common presentation of patello-femoral dysfunction and patients with this disorder represent a significant proportion attending a specialist knee clinic. There is an on-going debate as to the cause and best treatment for such patients. Previous studies on patella-femoral morphology have suggested patella maltracking plays an important part in the aetiology but there had been no studies correlating maltracking with articular cartilage change. Methods. We studied 147 consecutive patients (294 knees) aged between 10 and 63 presenting with anterior knee pain. All underwent MRI tracking scan of their knees as part of the routine investigations. We analysed the prevalence of maltracking with respect to gender, laterality and age groups, as well as patello-femoral articular cartilage changes. Results. 52% of patients were found to have maltracking, of which 75% were bilateral. Furthermore, 66% of patients with maltracking had radiological evidence of patellar articular cartilage changes, corresponding to 61% of 294 knees examined. While majority of these occur at lateral facet, a proportion of medial facet changes (16%) is also seen. More significantly, while 25% of knees from patients with maltracking under the age of 20 are found to have changes on the patella cartilage, this increases to 93% by the age of 50 or above, with step-wise increment per decade of age (p<0.01). Conclusion. Our results demonstrate a strong correlation between anterior knee pain symptoms, patella maltracking and changes in patello-femoral joint cartilages of varying severity. This has implications on the management of these patients and would suggest early correction of maltracking is indicated to prevent deterioration in the patello-femoral joint

Introduction. The current investigation includes a retrospective review of the experience of five Institutions with distal femur megaprostheses for tumor over a twenty year period, to analyze the incidence and etiology of failure, using a new classification system based upon the failure modes. Methods. Between 1974 and 2008, 2174 patients underwent primary limb preservation for a benign or malignant extremity tumor using a metallic megaprosthesis at five Institutions, 951 (43.7%) were distal femur replacements. Retrospective analysis of complications according to the Letson and Ruggieri Classification was performed and Kaplan-Meier curves of implant survival were defined. Segmental megaprosthetic reconstruction failures were categorized as mechanical and non-mechanical failures. Results. A total of 951 skeletally mature patients received a segmental endoprosthesis for the treatment of an oncologic condition. Overall 261 (27%) of the primary procedures were considered failures. There were 137 mechanical failures (14.4%): 12 (1.3%) Type 1 (soft tissue failure), 65 (6.8%) Type 2 (aseptic loosening), and 60 (6.3%) Type 3 (structural failure). Non-mechanical causes accounted for 124 failures (13%): 45 (4.7%)Type 4 (tumor progression) and 79 (8.3%) Type 5 (infection). The overall implant survival to all modes of failure was 77% at 10 years and 73% at 20 years. The implant survival to aseptic loosening was over 90% at 10 years. Conclusion. Most frequent cause of failure was infection followed by aseptic loosening and structural failure. The implant survival at long term was quite satisfactory

Background. Pseudotumours have been associated with metal-on-metal (MoM) hip replacements. We define it as a solid mass which may have cystic components that is neither neoplastic nor infectious in aetiology. The cause of a pseudotumour is not fully understood but could be due to excessive wear, metal hypersensitivity or due to an as-yet unknown cause. Aim. We present the retrieval analysis of early failure MoM hips revised for pain, loosening or a symptomatic mass. Tissues and implants were examined for the possible causes of failure and pseudotumour formation. Corrosion as a potential new cause for pseudotumour formation will be presented. Methods. A group of 16 MoM hip replacements were collected for retrieval analysis. Six of which had a pseudotumour. An Artificial Hip Profiler (Redlux Ltd) was used to measure wear. Edge loading was determined using the 3D wear data. Tissues were histologically evaluated using a 10-point ALVAL scoring system, which strongly suggests hypersensitivity (1). Cases were assigned to one of three categories: high wear (rates >5m/yr), hypersensitivity or corrosion. Results. Of the 6 pseudotumours, 3 had edge loading, 2 had high ALVAL scores and one had corrosion at the head taper junction. The high wear group, (3 cases) all demonstrated edge loading. Histology revealed more metal wear particles and macrophages, with a low ALVAL score in these cases. Two cases were found to have hypersensitivity with a high ALVAL score, more lymphocytes with less visible wear debris and macrophages. The wear rates were also lower, <4m/yr. One total hip replacement had corrosion at the junction between the head and adaptor taper for the stem. The bearings had low wear and the tissue had extensive necrosis as well as products of corrosion enclosed in fibrin (2). There was no suggestion of hypersensitivity (low ALVAL score). Conclusion. Pseudotumours can be caused by high wear, but if this is ruled out, a hypersensitivity or corrosion product reaction should be considered

Introduction. Numerous types of graft can be used for revision of anterior cruciate ligament (ACL) reconstruction. The goal of our studies was to analyze mid term outcomes of revision of anterior cruciate ligament reconstructions conducted by means of ipsilateral bone -patellar tendon -bone (B-PT-B) transplant. Materials and methods. We conducted a retrospective study on a consecutive series of 44 patients. All patients were operated on by the same senior surgeon in our institution between 2003 and 2009. All patients had undergone a first ACL reconstruction with B-PT-B transplant. They all had ACL revision under arthroscopic assistance and by means of ipsilateral B-PT-B transplant after a minimum of 18 months after primary surgery. At time of ACL revision, the mean patients age was 28 years (range, 17–49 years). The average postoperative follow up after revision was 55 months (range, 12–88 months). We had no patient lost to follow up. All patients were evaluated by an independent observer using IKDC scoring system and KT 2000. Results. The postoperative IKDC score averaged 78.2 (range, 41,4–97,7). 10 patients (22.7%) had their knee graded A, 25 patients (56.8%) grade B, 8 patients (18.2%) grade C and one patient (2.3%) grade D. The post operative maxi manual differential KT 2000 averaged 1,52 mm (range, −1mm/12mm). The identified aetiologies for poor clinical outcomes were menisectomy in the first ACL reconstruction (p<0.01) and articular cartilage lesions (ICRS grade III and IV) found during ACL revision. In most cases, return to sport activities was achieved but not at the same level. We had no specific complication after second harvesting of the patellar tendon. Discussion. The type of graft used in revision of ACL reconstructions is a controversy. In the literature, many studies reported the results of revision of ACL reconstructions but with poor methodology and few data for every type of graft. In our study, we found clinical results comparable to those classically reported in the literature. Clinical evaluation showed good control of the laxity and no specific patellar tendon complication. Conclusion. The clinical results of revision of ACL reconstructions is lower than in primary surgery. We did not noticed specific patellar tendon complication after second harvesting of BPTB transplant. The revision of ACL reconstruction with ipsilateral BPTB transplant showed good clinical results and good control of the anteroposterior laxity

Introduction. Since 2001 we use the flexible intramedullary nailing (FIN) in bone lengthening in children. This study estimates results of EF+FIN association considering the duration of external fixation and complications. Materials and Methods. Since 2001 we performed 294 bone lengthenings (338 segments of UL and LL) in 250 children 3 to 16 years old (11.01±0.23 in average). The length discrepancy was congenital in 163 cases, the sequelae of trauma or osteomyelitis were observed in 87 patients. In group I (195 cases) the Ilizarov fixator alone was applied, in group II the Ilizarov fixator (91 cases) or TSF® (8cases) were combined with FIN. The healing index was compared between the groups of the same etiology with similar type of distraction osteosynthesis. The date of consolidation corresponded to the day of removal of the external fixator, while intramedullary nails remained in place thus protecting the bone. Healing index was calculated by relating the duration of wearing of the external fixator (in days) and the amount of lengthening (in cm). Results. Reduction of the healing index is noted in each compared category. Thus, in congenital shortening in monofocal distraction osteosynthesis of the femur the healing index decreased from 29.8 (group I) to 20.4 days per cm, in bifocal tibial lengthening from 22.7 (group I) to 16.3d/cm (group II), in humeral lengthening – from 30.2 to 21.3 d/cm. In fact, it appears that the association of the external fixator of the Ilizarov type or TSF® with FIN allows to reduce the healing index significantly: in 12 of 16 compared categories the reduction of the index was from 20% to 40% or from 4.0 to 19.1 days per cm. In group I four cases of deep infection of soft tissues, 2 osteomyelitis, 21 fractures or deformities after frame removal were manifested. In group II – onlyone case of deformation after frame removal, absence of severe infectious complications, 8 cases of migration of the intramedullary wires. Discussion. FIN creates an elastic and resistant system during the lengthening. We even suggest that it stimulates the formation considering an apparent decrease of the healing index. On the other hand, the elasticity of nails prevents secondary fractures or deformations after frame removal. Conclusion. Combination of the circular EF and FIN in limb lengthening in children significantly decreases the duration of external fixation and the amount of severe infections and fractures

Aims. Currently, the most common approach for the management of a chronic PJI is a Two-Stage Replacement; because of success rates exceeding 90% when using an antibiotic impregnated cement spacer. Reliable information regarding the etiologic microorganism and its sensitivities is essential to select the antimicrobial therapy that should be used locally in the bone cement spacer during the first stage surgery as well as to select the appropriate microbiological systemic agent. Diagnostic algorithms focus to the importance of joint aspiration cultures although in the modern literature, preoperative joint aspiration has a broad range of values of sensitivity and the proportion of “dry-aspirations” is not well assessed. This low sensitivity of aspiration fluid samples in chronic-PJI is partly attributable to the fact that the majority of the microorganisms in these infections grow in biofilms attached to the implant. We have developed this biopsy technique in an effort to improve the identification rates of the causative organism. Materials and methods. A sample is harvested through a 4 mm bone trephine and the target is the bone-prosthesis gap. We have compared the results of preoperative PIB with the results of cultures from intra-operative tissue collected during the first stage surgery. In both cases a prolonged culture protocol (10 days) in enrichment media was used. On the basis of this relation, sensitivity, specificity, positive and negative predictive values and accuracy were calculated. Results. Twenty-four PIB were done on the 24 patients (10 hips and 14 knees) who subsequently underwent two-stage revision surgery because of high suspicion of PJI between January 2007 and December 2009. A retrospective analysis was performed in these 24 patients (13 women and 11 men) in the mean age of 70 years (from 63 to 88 years old). Nineteen of the cases were primary and 5 were revision arthroplasty. Nineteen patients (79%) were positive for infection from operative tissue cultures. The sensitivity was 0.79 (95% CI, 0.54–0.93); the specificity was 0.80 (95% CI, 0,30–0.99), the positive predictive value was 0.94 (95% CI, 0.67–0.99), the negative predictive value was 0.50 (95% CI, 17.5–82.5) and the accuracy was 0.79. Conclusion. PIB is a useful test to, preoperatively, isolate the infecting bacteria. The values of sensitivity, specificity and accuracy are on the average of the currently published with joint aspiration or biopsy samples cultures. Although comparative study is necessary we believe that the PIB could be useful in cases with high suspicion of PJI and negative joint aspiration cultures and in cases where no fluid is aspired from the joint, in order to preoperatively isolate the infecting bacteria

Introduction. The aim of the treatment of children with early onset scoliosis is controlling growth of the spine. Whatever the etiology, early progressive deformations require multiple stages of surgery usually performed every 6–12 months. One have to be reckoned with complications requiring additional surgical intervention. Objective. The aim of the study is to present a new method of surgical treatment of early onset scoliosis involving the implantation of specially constructed implants to allow three dimensional correction of spinal deformity with a preserved capacity to continue the growth of spine without distraction staged operations followed by final spondylodesis in mature spine. Material. The clinical material consists of homogeneous group of patients: 8 girls and a one boy aged 6 to 14 years (mean age = 9 years). The estimated group four children had a single-curve, four children had a double-curve, while one child was affected by congenital kyphosis. The follow up ranged from 2 to 17 months (mean = 13.5 months). Method. Efficacy of spinal deformity correction using a “growing implants” was estimated by Cobb andgle measurement of the curvature 1/before the operation, 2/after surgery and 3/follow up. Results. During surgery, all patients obtained a large correction of curvature ranging from 50% to 100% (on average −70%). The degree of correction was directly dependent on the size of the initial deformation of 62 to 120 ° (average 77 °). During the entire period of observation in four children we have not identified the loss of correction or fits within the limits of measurement error. In one child thirty degree-loss correction stemmed from too selective implantation of the implants. During additional surgery the stabilization was extended to the extra two motor segments witch resulting in full correction. In one patient, due to rapid growth, rods were needed to be replaced for longer, because of the risk of pulling out from the lower screws. In one case we observed further correction during follow up. Conclusions. Using the method we obtained a very good correction in the first stage of treatment. Maintenance of correction does not require any intermediate staged operating procedures. Patients do not require corrective brace. Using “growing implants” in the early onset scoliosis one avoid complications peculiar to current growth-sparing procedures. These patients would have had 15 lengthening procedures after their initial correction if treated by conventional growing rod methods

Introduction. Radiolucencies beneath the tibial component are well recognized in knee arthroplasty; the aetiology and significance are poorly understood. Non-progressive narrow radiolucencies with a sclerotic margin are thought not to be indicative of loosening. Factors which decrease the incidence of radiolucencies include cementless fixation and the use of pulse lavage. Leg/component alignment or BMI do not influence radiolucency. We are not aware of any studies that have looked at the effect of load type on radiolucency. The Oxford domed lateral tibial component was introduced to decrease the bearing dislocation rate that was unacceptably high with the flat tibial tray. However, the introduction of the domed tibial component alters the forces transmitted through the implant-cement-bone interface. As the Oxford UKR uses a fully congruent mobile bearing, the forces transmitted through the interface with a flat tray are compressive, except for the effect of friction. However, with the domed tibial component shear forces are introduced. The aim of this study was to assess the prevalence of radiolucency beneath the previous flat design and the new domed tibial tray. Patients and methods. A consecutive series of 248 cemented lateral UKRs (1999–2009) at a single institution were assessed. The first 55 were with a flat tibia and the subsequent 193 with a domed component. One year post-op radiographs were assessed, by two observers, for the presence (full or partial) and distribution of radiolucency. The distribution and thickness of each radiolucency. Cases were excluded for missing or poorly aligned radiographs. Results. In the flat group there were 42 patients (17 male, 25 female) with 42 joints. In the domed group there were 139 patients (44 male, 95 female) with 146 joints. There was a statistical significant difference between groups for the presence and extent of radiolucency (p<0.001). In the flat group, 6 (14%) had a full radiolucency and 18 (43%) had a partial radiolucency. 14 of the 18 partial radiolucencies involved the far lateral zones (1&2) and 3 partial radiolucencies involved the keel. In the domed group 6, (4.1%) had a full radiolucency and 13 (8.9%) had a partial radiolucency. All radiolucencies observed were less than 1 mm thick. Intra-class correlation for inter-observer agreement for assessment of radiolucency was 0.679. Discussion. The introduction the domed lateral tibial component results in a reduction in prevalence of radiolucency compared to a flat component. This suggests, as the mode of fixation is identical, that the forces across the tibial-cement-bone interface have a significant effect on the development of the tissue at that interface. In particular it suggests that compressive forces alone tend to cause soft tissue to be formed at the interface, whereas shear force causes bone