Between 1992 and 2000, 57 patients with 57 isolated fractures of the medial malleolus were treated conservatively by immobilisation in a cast. The results were assessed by examination, radiography and completion of the short form-36 questionnaire and American Orthopaedic Foot and Ankle Society ankle-hindfoot score. Of the 57 fractures 55 healed without further treatment. The mean combined dorsi- and plantar flexion was 52.3° (25° to 82°) and the mean short form-36 and American Orthopaedic Foot and Ankle Society scores 48.1 (28 to 60) and 89.8 (69 to 100), respectively. At review there was no evidence of medial instability, dermatological complications, malalignment of the mortise or of post-traumatic arthritis. Isolated fractures of the medial malleolus can obtain high rates of union and good functional results with conservative treatment. Operation should be reserved for bi- or trimalleolar fractures, open fractures, injuries which compromise the skin or those involving the plafond or for patients who develop painful nonunion

We report the cases of three children with chronic injuries of the medial tibial malleolus caused by traction injuries during sport. All three had the triad of swelling of the medial malleolus, tenderness over its anterior part, and pain on forced valgus movement of the foot. Radiographs showed bilateral accessory ossification centres and MRI demonstrated partial avulsion or avulsion fracture of the apophyseal cartilage and fragmentation of the accessory centres. A review of 134 young basketball players showed that 25% had tenderness of the anterior medial malleolus. This high rate indicates that traction apophysitis of the medial malleolus is not uncommon in children as a sports-related disorder

Aims. This study is a prospective, non-randomized trial for the treatment of fractures of the medial malleolus using lean, bioabsorbable, rare-earth element (REE)-free, magnesium (Mg)-based biodegradable screws in the adult skeleton. Methods. A total of 20 patients with isolated, bimalleolar, or trimalleolar ankle fractures were recruited between July 2018 and October 2019. Fracture reduction was achieved through bioabsorbable Mg-based screws composed of pure Mg alloyed with zinc (Zn) and calcium (Ca) ( Mg-Zn0.45-Ca0.45, in wt.%; ZX00). Visual analogue scale (VAS) and the presence of complications (adverse events) during follow-up (12 weeks) were used to evaluate the clinical outcomes. The functional outcomes were analyzed through the range of motion (ROM) of the ankle joint and the American Orthopaedic Foot and Ankle Society (AOFAS) score. Fracture reduction and gas formation were assessed using several plane radiographs. Results. The follow-up was performed after at least 12 weeks. The mean difference in ROM of the talocrural joint between the treated and the non-treated sites decreased from 39° (SD 12°) after two weeks to 8° (SD 11°) after 12 weeks (p ≤ 0.05). After 12 weeks, the mean AOFAS score was 92.5 points (SD 4.1). Blood analysis revealed that Mg and Ca were within a physiologically normal range. All ankle fractures were reduced and stabilized sufficiently by two Mg screws. A complete consolidation of all fractures was achieved. No loosening or breakage of screws was observed. Conclusion. This first prospective clinical investigation of fracture reduction and fixation using lean, bioabsorbable, REE-free ZX00 screws showed excellent clinical and functional outcomes. Cite this article: Bone Joint Res 2020;9(8):477–483

McFarland fractures of the medial malleolus in children, also classified as Salter–Harris Type III and IV fractures, are associated with a high incidence of premature growth plate arrest. In order to identify prognostic factors for the development of complications we reviewed 20 children with a McFarland fracture that was treated surgically, at a mean follow-up of 8.9 years (3.5 to 17.4). Seven children (35%) developed premature growth arrest with angular deformity. The mean American Orthopaedic Foot and Ankle Society Ankle-Hindfoot Scale for all patients was 98.3 (87 to 100) and the mean modified Weber protocol was 1.15 (0 to 5). There was a significant correlation between initial displacement (p = 0.004) and operative delay (p = 0.007) with premature growth arrest. Both risk factors act independently and additively, such that all children with both risk factors developed premature arrest whereas children with no risk factor did not. We recommend that fractures of the medial malleolus in children should be treated by anatomical reduction and screw fixation within one day of injury. Cite this article: Bone Joint J 2013;95-B:419–23

Aims. The morphology of medial malleolar fracture is highly variable and difficult to characterize without 3D reconstruction. There is also no universally accepeted classification system. Thus, we aimed to characterize fracture patterns of the medial malleolus and propose a classification scheme based on 3D CT reconstruction. Methods. We retrospectively reviewed 537 consecutive cases of ankle fractures involving the medial malleolus treated in our institution. 3D fracture maps were produced by superimposing all the fracture lines onto a standard template. We sliced fracture fragments and the standard template based on selected sagittal and coronal planes to create 2D fracture maps, where angles α and β were measured. Angles α and β were defined as the acute angles formed by the fracture line and the horizontal line on the selected planes. Results. A total of 121 ankle fractures were included. We revealed several important fracture features, such as a high correlation between posterior collicular fractures and posteromedial fragments. Moreover, we generalized the fracture geometry into three recurrent patterns on the coronal view of 3D maps (transverse, vertical, and irregular) and five recurrent patterns on the lateral view (transverse, oblique, vertical, Y-shaped, and irregular). According to the fracture geometry on the coronal and lateral view of 3D maps, we subsequently categorized medial malleolar fractures into six types based on the recurrent patterns: anterior collicular fracture (27 type I, 22.3%), posterior collicular fracture (12 type II, 9.9%), concurrent fracture of anterior and posterior colliculus (16 type III, 13.2%), and supra-intercollicular groove fracture (66 type IV, 54.5%). Therewere three variants of type IV fractures: transverse (type IVa), vertical (type IVb), and comminuted fracture (type IVc). The angles α and β varied accordingly. Conclusion. Our findings yield insight into the characteristics and recurrent patterns of medial malleolar fractures. The proposed classification system is helpful in understanding injury mechanisms and guiding diagnosis, as well as surgical strategies. Cite this article: Bone Joint J 2021;103-B(5):931–938

Abstract. The medial malleolus, once believed to be the primary stabilizer of the ankle, has been the topic of conflicting clinical and biomechanical data for many decades. Despite the relevant surgical anatomy being understood for almost 40 years, the optimal treatment of medial malleolar fractures remains unclear, whether the injury occurs in isolation or as part of an unstable bi- or trimalleolar fracture configuration. Traditional teaching recommends open reduction and fixation of medial malleolar fractures that are part of an unstable injury. However, there is recent evidence to suggest that nonoperative management of well-reduced fractures may result in equivalent outcomes, but without the morbidity associated with surgery. This review gives an update on the relevant anatomy and classification systems for medial malleolar fractures and an overview of the current literature regarding their management, including surgical approaches and the choice of implants. Cite this article: Bone Joint J 2019;101-B:512–521

Aims. The aims of this study were to evaluate the morphology of the ankle in patients with an osteochondral lesion of the talus using 3D CT, and to investigate factors that predispose to this condition. Patients and Methods. The study involved 19 patients (19 ankles) who underwent surgery for a medial osteochondral lesion (OLT group) and a control group of 19 healthy patients (19 ankles) without ankle pathology. The mean age was significantly lower in the OLT group than in the control group (27.0 vs 38.9 years; p = 0.02). There were 13 men and six women in each group. 3D CT models of the ankle were made based on Digital Imaging and Communications in Medicine (DICOM) data. The medial malleolar articular and tibial plafond surface, and the medial and lateral surface area of the trochlea of the talus were defined. The tibial axis-medial malleolus (TMM) angle, the medial malleolar surface area and volume (MMA and MMV) and the anterior opening angle of the talus were measured. Results. The mean TMM angle was significantly larger in the OLT group (34.2°, . sd. 4.4°) than in the control group (29.2°, . sd. 4.8°; p = 0.002). The mean MMA and MMV were significantly smaller in the OLT group than in the control group (219.8 mm. 2. , . sd. 42.4) vs (280.5 mm. 2. , . sd. 38.2), and (2119.9 mm. 3. , . sd. 562.5) vs (2646.4 mm. 3. , . sd. 631.4; p < 0.01 and p = 0.01, respectively). The mean anterior opening angle of the talus was significantly larger in the OLT group than in the control group (15.4°, . sd. 3.9°) vs (10.2°, . sd. 3.6°; p < 0.001). Conclusion. 3D CT measurements showed that, in patients with a medial osteochondral lesion of the talus, the medial malleolus opens distally, the MMA and MMV are small, and the anterior opening angle of the talus is large. This suggests that abnormal morphology of the ankle predisposes to the development of osteochondral lesions of the talus. Cite this article: Bone Joint J 2018;100-B:1487–90

Introduction. Unstable ankle fractures are routinely managed operatively. Due to soft-tissue and implant related complications, there has been recent literature reporting on the non-operative management of well-reduced medial malleolus fractures following fibular stabilisation, but with limited evidence supporting routine application. This trial assessed the superiority of internal fixation of well-reduced (displacement ≤2mm) medial malleolus fractures compared with non-fixation following fibular stabilisation. Methods and participants. Superiority, pragmatic, parallel, prospective randomised clinical trial conducted over a four year period. A total of 154 adult patients with a bi- or trimalleolar fractures were recruited from a single centre. Open injuries and vertical medial malleolar fractures were excluded. Following fibular stabilisation, patients were randomised intra-operatively on a 1:1 basis to fixation or non-fixation after satisfactory fluoroscopic fracture reduction was confirmed. The primary outcome was the Olerud Molander Ankle Score (OMAS) at one-year post-randomisation. Complications and radiographic outcomes were documented over the follow-up period. Results. Among 154 participants (mean age, 56.5 years; 119 women [77%]), 144 [94%] completed the trial. At one-year the median OMAS was 80 (IQR, 60–90) in the fixation group compared with 72.5 (IQR, 55–90) in the non-fixation group (p=0.17). Complication rates were comparable. Significantly more patients in the non-fixation group developed a radiographic non-union (20% vs 0%; p<0.001), with the majority (n=8/13) clinically asymptomatic and one patient required surgical re-intervention for this. Fracture type and reduction quality appeared to influence fracture union and patient outcome. Conclusions. In this randomised clinical trial comparing internal fixation of well-reduced medial malleolus fractures with non-fixation, following fibular stabilisation, fixation was not superior according to the primary outcome. However, 1 in 5 patients following non-fixation developed a radiographic non-union and whilst the re-intervention rate to manage this was low, the future implications require surveillance. These results may support selective non-fixation of anatomically reduced medial malleolus fractures

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. Methods. We retrospectively analyzed patients who underwent hindfoot Charcot reconstruction with an intramedullary nail between January 2007 and December 2019 in our unit. Patient demographic details, comorbidities, weightbearing status, and postoperative complications were noted. Metalwork breakage, nonunion, deformity recurrence, concurrent midfoot reconstruction, and the measurements related to intramedullary nail were also recorded. Results. There were 70 patients with mean follow-up of 54 months (SD 26). Overall, 51 patients (72%) and 52 patients (74%) were fully weightbearing at one year postoperatively and at final follow-up, respectively. The overall hindfoot union rate was 83% (58/70 patients). Age, BMI, glycated haemoglobin, and prior revascularization did not affect union. The ratio of nail diameter and isthmus was greater in the united compared to the nonunited group (0.90 (SD 0.06) and 0.86 (SD 0.09), respectively; p = 0.034). In those with a supplementary hindfoot compression screw, there was a 95% union rate (19/20 patients), compared to 78% in those without screws (39/50 patients; p = 0.038). All patients with a miss-a-nail hindfoot compression screw went on to union. Hindfoot metalwork failure was seen in 13 patients (19%). An intact medial malleolus was found more frequently in those with intact metalwork ((77% (44/57 patients) vs 54% (7/13 patients); p = 0.022) and in those with union ((76% (44/58 patients) vs 50% (6/12 patients); p = 0.018). Broken metalwork occurred more frequently in patients with nonunions (69% (9/13 patients) vs 9% (5/57 patients); p < 0.001) and midfoot deformity recurrence (69% (9/13 patients) vs 9% (5/57 patients); p < 0.001). Conclusion. Rates of hindfoot union and intact metalwork were noted in over 80% of patients. Union after hindfoot reconstruction occurs more frequently with an isthmic fit of the intramedullary nail and supplementary hindfoot screws. An intact medial malleolus is protective against nonunion and hindfoot metalwork failure. Cite this article: Bone Joint J 2022;104-B(6):703–708

Aims. The ideal management of acute syndesmotic injuries in elite athletes is controversial. Among several treatment methods used to stabilize the syndesmosis and facilitate healing of the ligaments, the use of suture tape (InternalBrace) has previously been described. The purpose of this study was to analyze the functional outcome, including American Orthopaedic Foot & Ankle Society (AOFAS) scores, knee-to-wall measurements, and the time to return to play in days, of unstable syndesmotic injuries treated with the use of the InternalBrace in elite athletes. Methods. Data on a consecutive group of elite athletes who underwent isolated reconstruction of the anterior inferior tibiofibular ligament using the InternalBrace were collected prospectively. Our patient group consisted of 19 elite male athletes with a mean age of 24.5 years (17 to 52). Isolated injuries were seen in 12 patients while associated injuries were found in seven patients (fibular fracture, medial malleolus fracture, anterior talofibular ligament rupture, and posterior malleolus fracture). All patients had a minimum follow-up period of 17 months (mean 27 months (17 to 35)). Results. All patients returned to their pre-injury level of sports activities. One patient developed a delayed union of the medial malleolus. The mean return to play was 62 days (49 to 84) for isolated injuries, while the patients with concomitant injuries returned to play in a mean of 104 days (56 to 196). The AOFAS score returned to 100 postoperatively in all patients. Knee-to-wall measurements were the same as the contralateral side in 18 patients, while one patient lacked 2 cm compared to the contralateral side. Conclusion. This study suggests the use of the InternalBrace in the management of unstable syndesmotic injuries offers an alternative method of stabilization, with good short-term results, including early return to sports in elite athletes. Cite this article: Bone Joint J 2022;104-B(1):68–75

The June 2024 Trauma Roundup. 360. looks at: Skin antisepsis before surgical fixation of limb fractures; Comparative analysis of intramedullary nail versus plate fixation for fibula fracture in supination external rotation type IV ankle injury; Early weightbearing versus late weightbearing after intramedullary nailing for distal femoral fracture (AO/OTA 33) in elderly patients: a multicentre propensity-matched study; Long-term outcomes with spinal versus general anaesthesia for hip fracture surgery; Operative versus nonoperative management of unstable medial malleolus fractures: a randomized clinical trial; Impact of smoking status on fracture-related infection characteristics and outcomes; Reassessing empirical antimicrobial choices in fracture-related infections; Development and validation of the Nottingham Trauma Frailty Index (NTFI) for older trauma patients

Ensuring correct rotation of the femoral component is a challenging aspect of patellofemoral replacement surgery. Rotation equal to the epicondylar axis or marginally more external rotation is acceptable. Internal rotation is associated with poor outcomes. This paper comprises two studies evaluating the use of the medial malleolus as a landmark to guide rotation. We used 100 lower-leg anteroposterior radiographs to evaluate the reliability of the medial malleolus as a landmark. Assessment was made of the angle between the tibial shaft and a line from the intramedullary rod entry site to the medial malleolus. The femoral cut was made in ten cadaver knees using the inferior tip of the medial malleolus as a landmark for rotation. Rotation of the cut relative to the anatomical epicondylar axis was assessed using CT. The study of radiographs found the position of the medial malleolus relative to the tibial axis is consistent. Using the inferior tip of the medial malleolus in the cadaver study produced a mean external rotation of 1.6° (0.1° to 3.7°) from the anatomical epicondylar axis. Using the inferior tip of the medial malleolus to guide the femoral cutting jig avoids internal rotation and introduces an acceptable amount of external rotation of the femoral component

Aims. Paediatric triplane fractures and adult trimalleolar ankle fractures both arise from a supination external rotation injury. By relating the experience of adult to paediatric fractures, clarification has been sought on the sequence of injury, ligament involvement, and fracture pattern of triplane fractures. This study explores the similarities between triplane and trimalleolar fractures for each stage of the Lauge-Hansen classification, with the aim of aiding reduction and fixation techniques. Methods. Imaging data of 83 paediatric patients with triplane fractures and 100 adult patients with trimalleolar fractures were collected, and their fracture morphology was compared using fracture maps. Visual fracture maps were assessed, classified, and compared with each other, to establish the progression of injury according to the Lauge-Hansen classification. Results. Four stages of injury in triplane fractures, resembling the adult supination external rotation Lauge-Hansen stages, were observed. Stage I consists of rupture of the anterior syndesmosis or small avulsion of the anterolateral tibia in trimalleolar fractures, and the avulsion of a larger Tillaux fragment in triplanes. Stage II is defined as oblique fracturing of the fibula at the level of the syndesmosis, present in all trimalleolar fractures and in 30% (25/83) of triplane fractures. Stage III is the fracturing of the posterior malleolus. In trimalleolar fractures, the different Haraguchi types can be discerned. In triplane fractures, the delineation of the posterior fragment has a wave-like shape, which is part of the characteristic Y-pattern of triplane fractures, originating from the Tillaux fragment. Stage IV represents a fracture of the medial malleolus, which is highly variable in both the trimalleolar and triplane fractures. Conclusion. The paediatric triplane and adult trimalleolar fractures share common features according to the Lauge-Hansen classification. This highlights that the adolescent injury arises from a combination of ligament traction and a growth plate in the process of closing. With this knowledge, a specific sequence of reduction and optimal screw positions are recommended. Cite this article: Bone Joint J 2024;106-B(9):1008–1014

Introduction. Surgical reconstruction of deformed Charcot feet carries high risk of non-union, metalwork failure and deformity recurrence. The primary aim of this study was to identify the factors contributing to these complications following hindfoot Charcot reconstructions. Methods. We retrospectively analysed patients who underwent hindfoot Charcot reconstruction with an intramedullary nail between 2007 and 2019 in our unit. Patient demographics, co-morbidities, weightbearing status and post-operative complications were noted. Metalwork breakage, non-union, deformity recurrence, concurrent midfoot reconstruction and the measurements related to intramedullary nail were also recorded. Results. There were 70 patients with mean follow up of 50±26 months. Seventy-two percent were fully weightbearing at 1 year post-operatively. The overall union rate was 83%. Age, BMI, HbA1c and peripheral vascular disease did not affect union. The ratio of nail diameter and isthmus was greater in the united compared to the non-united group (0.90±0.06 and 0.86±0.09, respectively; p = 0.03). Supplemental compression devices were used for 33% of those in the united compared to 8% in the non-united group (p = 0.04). All patients in the non-union group did not have a miss-a-nail screw. Metalwork failure was seen in 13 patients(19%). There was a significantly greater distal screw metalwork failure in those with supplementary bridging of tibia to midfoot (23% vs. 3%; p = 0.001). An intact medial malleolus was found more frequently in those with intact metalwork (77% vs. 54%, respectively; p = 0.02) and those with union (76% vs. 50%; p = 0.02). Broken metalwork occurred more frequently in patients with non-unions (69% vs. 8%; p < 0.001) and deformity recurrence (69% vs. 9%; p < 0.001). Conclusion. Satisfactory clinical and radiographic outcomes occur in over 80% of patients. Union after hindfoot reconstruction occurs more frequently with an isthmic fit of the intramedullary nail, supplementary compression and miss-a-nail screws. An intact medial malleolus is protective against non-union and metalwork failure. Broken metalwork is linked to deformity recurrence and non-union

Aims. The purpose of this study was to assess the success rate and functional outcomes of bone grafting for periprosthetic bone cysts following total ankle arthroplasty (TAA). Additionally, we evaluated the rate of graft incorporation and identified associated predisposing factors using CT scan. Methods. We reviewed a total of 37 ankles (34 patients) that had undergone bone grafting for periprosthetic bone cysts. A CT scan was performed one year after bone grafting to check the status of graft incorporation. For accurate analysis of cyst volumes and their postoperative changes, 3D-reconstructed CT scan processed with 3D software was used. For functional outcomes, variables such as the Ankle Osteoarthritis Scale score and the visual analogue scale for pain were measured. Results. Out of 37 ankles, graft incorporation was successful in 30 cases. Among the remaining seven cases, four (10.8%) exhibited cyst re-progression, so secondary bone grafting was needed. After secondary bone grafting, no further progression has been noted, resulting in an overall 91.9% success rate (34 of 37) at a mean follow-up period of 47.5 months (24 to 120). The remaining three cases (8.1%) showed implant loosening, so tibiotalocalcaneal arthrodesis was performed. Functional outcomes were also improved after bone grafting in all variables at the latest follow-up (p < 0.05). The mean incorporation rate of the grafts according to the location of the cysts was 84.8% (55.2% to 96.1%) at the medial malleolus, 65.1% (27.6% to 97.1%) at the tibia, and 81.2% (42.8% to 98.7%) at the talus. Smoking was identified as a significant predisposing factor adversely affecting graft incorporation (p = 0.001). Conclusion. Bone grafting for periprosthetic bone cysts following primary TAA is a reliable procedure with a satisfactory success rate and functional outcomes. Regular follow-up, including CT scan, is important for the detection of cyst re-progression to prevent implant loosening after bone grafting. Cite this article: Bone Joint J 2024;106-B(5):475–481

Medial malleolar stress fractures are uncommon even in the sporting population. They tend to occur almost exclusively in athletes involved in sports involving running and jumping. We believe that stress fractures of the medial malleolus may be the end stage of chronic anteromedial ankle impingement in elite running and jumping athletes. Anterior impingement spurs are thought to be caused by repetitive microtrauma at the limit of dorsiflexion causing subperiosteal haemorrhage and subsequent ossification. More specifically the lower surface of the anterior tibia and the anterior part of the medial malleolus undergo similar trauma during severe supination injuries. Repetitive trauma to the cartilage from the kicking action in soccer is also thought to play a part, the cartilage responding by the formation of scar tissue and subsequent calcification. We present five cases of elite athletes (three AFLplayers, one sprinter and one A Grade cricketer) who presented to our establishment with vertical stress fractures of the medial malleolus over a three year period (2004–7). In each case preoperative imaging revealed an anteromedial bony spur on the tibia. All patients had the fractures internally fixed and at the same sitting had arthroscopic debridement of the impingement spur. Average time to union was 10.2 weeks (6–16). At most recent review (average 18 months (8–37)) all fractures had united and all patients had resumed sporting activity. No patient had suffered a further fracture of the medial malleolus. We believe this region of impingement causes premature abutment of the talus on the tibia in the supination-adduction motion that in severe trauma leads to the vertical fracture through the medial malleolus according to the Lauge-Hansen classification. We therefore feel it should be addressed at the time of fracture fixation to reduce the re-fracture rate

There is limited literature available looking into circumstances surrounding the development of stress fracture of the medial and lateral malleoli after ankle replacement. We present the preliminary results of a prospective study examining the effect of ankle replacement upon local bone mineral density and the phenomenon of stress shielding. We aimed to assess the effect of ankle replacement loading of the medial and lateral malleoli, by analysing the Bone Mineral Density (BMD) of the medial and lateral malleoli before and after Mobility total ankle replacement. Ten consecutive patients undergoing Mobility total ankle replacement for osteoarthritis had pre-operative bone densitometry scans of the ankle, repeated at 6 months after surgery. The bone mineral density of a 2 cm square area within the medial malleolus and lateral malleolus was measured. The pre-operative and postoperative bone densitometry scans were compared. The relation between the alignment of the tibial component and the bone mineral density of the malleoli was also analysed. The mean preoperative BMD within the medial malleolus improved from 0.57g/cm2 to mean 6 months postoperative BMD of 0.62g/cm2. The mean preoperative BMD within the lateral malleolus decreased from 0.39g/cm2 to a mean 6 months postoperative of 0.33g/cm2. The mean alignment of the tibial component was 88.50 varus (range 850 varus to 940 valgus). However, there was no correlation between the alignment of the tibial component and the bone mineral density on the medial malleolus (r = 0.09, p = 0.865). The absence of stress shielding around the medial malleolus indicates that ankle replacements implanted within the accepted limits for implant alignment, load the medial malleolus. However, there was stress shielding over the lateral malleolus resulting in decreased BMD in the lateral malleolus

Introduction: There is limited literature available looking into circumstances surrounding the development of stress fracture of the medial and lateral malleoli after ankle replacement. We present the preliminary results of a prospective study examining the effect of ankle replacement upon local bone mineral density and the phenomenon of stress shielding. Aim: To assess the effect of ankle replacement loading of the medial and lateral malleoli, by analysing the BMD of the medial and lateral malleoli before and after Mobility total ankle replacement. Methodology: Ten consecutive patients undergoing Mobility total ankle replacement for osteoarthritis had pre-operative bone densitometry scans of the ankle, repeated at 6 and 12 months after surgery. The bone mineral density of a 2 cm square area within the medial malleolus and lateral malleolus was measured. The pre-operative and post-operative bone densitometry scans were compared. The relation between the alignment of the tibial component and the bone mineral density of the malleoli was also analysed. Results: The mean preoperative BMD within the medial malleolus improved from 0.58g/cm2 to mean 6 months postoperative BMD of 0.59g/cm2 and 0.60g/cm2 at 12 months. The mean preoperative BMD within the lateral malleolus decreased from 0.40g/cm2 to a mean 6 months postoperative BMD of 0.34g/cm2. However the BMD over the lateral malleolus increased to 0.36g/cm2 at 12 months. The mean alignment of the tibial component was 88.5° varus (85° varus to 94° valgus). There was no correlation between the alignment of the tibial component and the bone mineral density on the medial malleolus (r = 0.09, p = 0.865). Conclusion: The absence of stress shielding around the medial malleolus indicates that TAR implanted within the accepted limits for implant alignment, load the medial malleolus. However, there was stress shielding over the lateral malleolus resulting in decreased BMD in the lateral malleolus

Introduction: There is limited literature available looking into circumstances surrounding the development of stress fracture of the medial and lateral malleoli after ankle replacement. We present the preliminary results of a prospective study examining the effect of ankle replacement upon local bone mineral density and the phenomenon of stress shielding. Aim: To assess the effect of ankle replacement loading of the medial and lateral malleoli, by analysing the BMD of the medial and lateral malleoli before and after Mobility total ankle replacement. Methodology: Ten consecutive patients undergoing Mobility total ankle replacement for osteoarthritis had pre-operative bone densitometry scans of the ankle, repeated at 6 months after surgery. The bone mineral density of a 2 cm square area within the medial malleolus and lateral malleolus was measured. The pre-operative and post-operative bone densitometry scans were compared. The relation between the alignment of the tibial component and the bone mineral density of the malleoli was also analysed. Results: The mean preoperative BMD within the medial malleolus improved from 0.57g/cm2 to mean 6 months postoperative BMD of 0.62g/cm2. The mean preoperative BMD within the lateral malleolus decreased from 0.39g/cm2 to a mean 6 months postoperative BMD of 0.33g/cm2. The mean alignment of the tibial component was 88.50 varus (range 850 varus to 940 valgus). However, there was no correlation between the alignment of the tibial component and the bone mineral density on the medial malleolus (r = 0.09, p = 0.865). Conclusion: The absence of stress shielding around the medial malleolus indicates that ankle replacements implanted within the accepted limits for implant alignment, load the medial malleolus. However, there was stress shielding over the lateral malleolus resulting in decreased BMD in the lateral malleolus