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.

In this retrospective study, we assessed the outcome in 99 patients who underwent reconstruction of the lateral ligaments of the ankle for chronic anterolateral instability with a minimum follow-up of 15 years. Two techniques were compared: 54 patients had an anatomical reconstruction (AR group) and 45 had an Evans tenodesis (ET group). They were followed up for 19.9 ± 3.6 years and 21.8 ± 4.6 years, respectively. During follow-up, seven patients in the AR group and 17 in the ET group required a further operation (p = 0.004). At follow-up, significantly more patients (n = 15) in the ET group had limited dorsiflexion than in the AR group (n = 6, p = 0.007) and 18 in the ET group had a positive anterior drawer test compared with seven in the AR group (p = 0002). In the ET group 27 had tenderness on palpation of the ankle compared with 15 in the AR group (p = 0.001). Stress radiographs showed ligamentous laxity significantly more often in the ET group (n = 30) than in the AR group (n = 13, p < 0.001). The mean values for talar tilt and anterior talar translation were significantly higher in the ET group than in the AR group (p < 0.001, p = 0.007, respectively). There were degenerative changes on standard radiographs in 32 patients in the AR group and 35 in the ET group (p = 0.05). Four patients in the ET group had developed severe osteoarthritis compared with none in the AR group (p = 0.025). Assessment of functional stability revealed a mean Karlsson score of 83.7 ± 10.4 points in the AR group and 67.0 ± 15.8 points in the ET group (p < 0.001). According to the Good rating system, 43 patients in the AR group had good or excellent results compared with 15 in the ET group (p < 0.001). Compared with anatomical reconstruction, the Evans tenodesis does not prevent laxity in a large number of patients. Long-standing ligamentous laxity leads to degenerative change in the ankle, resulting in chronic pain, limited dorsiflexion and further operations. The functional result deteriorates more rapidly after the Evans tenodesis than after anatomical reconstruction

Aims: The objective of this study was to assess whether anatomical placement of the prosthesis, in shoulder hemi-arthroplasty for fracture of the humeral head, is important to the clinical outcome. Methods: Sixteen patients, with a fracture of the upper humerus treated with hemi-arthroplasty, were followed-up 45.7±15.1 (20–72) months after surgery. The results were assessed using the Constant-Murley scale. The mean score was 75.8±15.7% (54–96%). At the time of their last follow up they underwent CT of the fractured and sound humerus, in order to be measured differences in humeral length and retroversion using special software. Correlation between these differences and the clinical outcome, as it was measured with the Constant-Murley scale, was performed. Results: The mean difference in retroversion was 8.7 degrees and the mean difference in length was 0.65cm, between fractured and sound humerus in our patients. We have achieved a very good þnal outcome (Constant score more than 71%) in patients with difference in retroversion less than 10 degrees and difference in length less then 14mm, between fractured and sound humerus. Conclusions: Restoration of the humeral length and retroversion is very important in shoulder hemiarthroplasty for fracture of the humeral head. Only small differences from the optimum length are well tolerated while only big differences from the optimum retroversion are likely to affect signiþcantly the clinical outcome. We attribute the very good clinical outcome in our series to the quality of the anatomical reconstruction that was performed despite the fact that our sample is small and we cannot have powerful statistics

There have been few reports with efficient treatments for neglected distal tibiofibular syndesmosis disruption. Here we will report four cases of successful anatomical reconstruction with autologous gracilis tendon, using the interference fit anchoring (IFA) system. All four cases were males between 20 and 58 years of age at the time of surgery (mean age 36 years). The post-injury period to surgery was between 7 and 59 months (mean 20.1 months), with the consultation period being from 5 to 19 months (mean 9.5 months). Radiographs at the time of injuries were all malleolar fractures of pronation-external rotation (PE) stage 3 in the Lauge-Hansen classification. Stress tests for distal tibiofibular syndesmosis were positive in all cases (dilation more than 2 mm). Arthroscopic drilling was conducted in two cases with a cartilaginous injury of trochlea of talus. Distal tibiofibular syndesmosis was anatomically repositioned and was fixed with screws after bony and soft tissues within the tibiofibular syndesmosis were removed and fibular adhesion was dissected. Ipsilateral autologous gracilis tendon was passed through foramen in the insertion of the anterior inferior tibiofibular tendon on tibia and fibula, and was fixated using the IFA system. The preoperative Japanese society for surgery of the foot (JSSF) score was from 26 to 74 points (mean 43.5) and postoperative JSSF score was from 67 to 100 (mean 89.5). In a case where there was a poor outcome, five years of post injury had passed before the surgery. Although the JSSF score improved to 67 points postoperatively (from the preoperative score of 26) in this case, arthroscopic arthrodesis was conducted 5 months postoperatively due to persistent pain. Anatomical reconstruction with autologous gracilis tendon using the IFA system showed a favorable functional prognosis overall. However, there was a case with progressive degenerated changes of injured distal tibiofibular syndesmosis due to a prolonged post-injury period resulted in a poor outcome

Aims. The aim of this study was to examine the implant accuracy of custom-made partial pelvis replacements (PPRs) in revision total hip arthroplasty (rTHA). Custom-made implants offer an option to achieve a reconstruction in cases with severe acetabular bone loss. By analyzing implant deviation in CT and radiograph imaging and correlating early clinical complications, we aimed to optimize the usage of custom-made implants. Methods. A consecutive series of 45 (2014 to 2019) PPRs for Paprosky III defects at rTHA were analyzed comparing the preoperative planning CT scans used to manufacture the implants with postoperative CT scans and radiographs. The anteversion (AV), inclination (IC), deviation from the preoperatively planned implant position, and deviation of the centre of rotation (COR) were explored. Early postoperative complications were recorded, and factors for malpositioning were sought. The mean follow-up was 30 months (SD 19; 6 to 74), with four patients lost to follow-up. Results. Mean CT defined discrepancy (Δ) between planned and achieved AV and IC was 4.5° (SD 3°; 0° to 12°) and 4° (SD 3.5°; 1° to 12°), respectively. Malpositioning (Δ > 10°) occurred in five hips (10.6%). Native COR reconstruction was planned in 42 cases (93%), and the mean 3D deviation vector was 15.5 mm (SD 8.5; 4 to 35). There was no significant influence in malpositioning found for femoral stem retention, surgical approach, or fixation method. Conclusion. At short-term follow-up, we found that PPR offers a viable solution for rTHA in cases with massive acetabular bone loss, as highly accurate positioning can be accomplished with meticulous planning, achieving anatomical reconstruction. Accuracy of achieved placement contributed to reduced complications with no injury to vital structures by screw fixation. Cite this article: Bone Joint J 2022;104-B(10):1110–1117

Aims. The aim of this study was to compare open reduction and internal fixation (ORIF) with revision surgery for the surgical management of Unified Classification System (UCS) type B periprosthetic femoral fractures around cemented polished taper-slip femoral components following primary total hip arthroplasty (THA). Methods. Data were collected for patients admitted to five UK centres. The primary outcome measure was the two-year reoperation rate. Secondary outcomes were time to surgery, transfusion requirements, critical care requirements, length of stay, two-year local complication rates, six-month systemic complication rates, and mortality rates. Comparisons were made by the form of treatment (ORIF vs revision) and UCS type (B1 vs B2/B3). Kaplan-Meier survival analysis was performed with two-year reoperation for any reason as the endpoint. Results. A total of 317 periprosthetic fractures (in 317 patients) with a median follow-up of 3.6 years (interquartile range (IQR) 2.0 to 5.4) were included. The fractures were type B1 in 133 (42.0%), B2 in 170 (53.6%), and B3 in 14 patients (4.4%). ORIF was performed in 167 (52.7%) and revision in 150 patients (47.3%). The two-year reoperation rate (15.3% vs 7.2%; p = 0.021), time to surgery (4.0 days (IQR 2.0 to 7.0) vs 2.0 days (IQR 1.0 to 4.0); p < 0.001), transfusion requirements (55 patients (36.7%) vs 42 patients (25.1%); p = 0.026), critical care requirements (36 patients (24.0%) vs seven patients (4.2%); p < 0.001) and two-year local complication rates (26.7% vs 9.0%; p < 0.001) were significantly higher in the revision group. The two-year rate of survival was significantly higher for ORIF (91.9% (standard error (SE) 0.023%) vs 83.9% (SE 0.031%); p = 0.032) compared with revision. For B1 fractures, the two-year reoperation rate was significantly higher for revision compared with ORIF (29.4% vs 6.0%; p = 0.002) but this was similar for B2 and B3 fractures (9.8% vs 13.5%; p = 0.341). The most common indication for reoperation after revision was dislocation (12 patients; 8.0%). Conclusion. Revision surgery has higher reoperation rates, longer surgical waiting times, higher transfusion requirements, and higher critical care requirements than ORIF in the management of periprosthetic fractures around polished taper-slip femoral components after THA. ORIF is a safe option providing anatomical reconstruction is achievable. Cite this article: Bone Joint J 2023;105-B(2):124–134

Introduction

Implantation of total hip replacement (THR) remains a concern in patients with developmental dysplasia of the hip (DDH) because of bone deformities and previous surgeries. In this frequently young population, anatomical reconstruction of the hip rotation centre is particularly challenging in severe, low and high dislocation, DDH. The basic principles of the technique and the implant selection may affect the long-term results.

The aim of the study was to compare surgical difficulties and outcome in patients who underwent THR due to arthritis secondary to moderate or severe DDH.

Introduction. Charcot neuroarthropathy is a debilitating condition that frequently leads to skeletal instability, and has an increased risk of ulceration leading to infection and amputation. However, surgical reconstruction may offer limb salvage and restauration of an ulcer-free, plantigrade stable foot for functional weight-bearing. We report on our case series according to a prospective protocol and analyse factors leading to a favourable outcome. Methods. We report a prospective follow-up of 62 patients undergoing Charcot reconstruction, May 2014- Jan 2022, by two surgeons. Peripheral vascular disease was routinely assessed using Duplex scan and major arterial disease was treated before reconstruction. Utilising 3D modelling, pre-operative planning and standardised osteotomies, we performed anatomical correction with radiological evidence. Definitive fixation was undertaken with internal fixation to stabilise the hindfoot. Multivariant analysis was performed to assess risk factors for failure (P>0.05 statistical significance). Results. 59 feet were included, 3 patients did not progress to definitive surgery and 3 patients had bilateral surgery. 62.7% patients were male with an average age of 56, 88.13% had Type 2 diabetes, 56% were hypertensive, 14% were on dialysis. Twenty (54.1%) single stage reconstructions had pre-operative ulceration, 3 pts had ischaemic heart disease and 36 pts had evidence of peripheral arterial disease. 81% of patients achieved normalisation of the 3 out of 4 anatomical angles (P<0.05). Two patients (3.1%) required metalwork removal for infection and limb salvage, 11 (18.6%) had delayed wound healing. Survivorship was 97% at 3yrs, and 94% at 6yrs, however if pre-existing vascular disease was present, it was 94% at 3yrs 85.3% at 6yrs. All patients were mobile at a 3 years mean follow up. Conclusion. Careful patient selection, multidisciplinary team and anatomic reconstruction led to predictable outcomes and functional limb salvage. Pre-operative vascular compromise led to a slight reduction in survivorship, but no major amputation

Aims

The aim of this prospective study was to evaluate the intermediate-term outcomes after revision anatomical ankle ligament reconstruction augmented with suture tape for a failed modified Broström procedure.

We performed a retrospective study to assess the long-term outcome of non-augmented anatomical direct repair of the lateral ankle ligaments, as originally described by Duquennoy et al, for the treatment of chronic lateral instability of the ankle. This procedure aims to restore stability by the re-insertion and tightening of the original talofibular and calcaneofibular ligaments without division of the ligament. We examined the outcome in terms of the post-operative quality of life, the function of the joint and the development of osteoarthritis.

Between 1985 and 2002, 23 patients (11 males, 12 females) with a mean age of 32 years (15 to 58) who had undergone this procedure completed the Short-Form 36 assessment of quality of life and the Olerud and Molander Ankle score for the subjective evaluation of symptoms. Clinical re-evaluation, including examination of the ankle and the completion of the American Orthopaedic Foot and Ankle Society questionnaire was performed on 21 patients after a mean follow-up of 13 years (3 to 22.2). At the final follow-up radiographs of both ankles were taken to assess the development of osteoarthritis.

The mean total Short-Form 36 and Olerud and Molander Ankle scores in 23 patients at final follow-up were 79.6 points (37 to 100) and 81.6 points (40 to 100), respectively. The mean total post-operative American Orthopaedic Foot and Ankle Society score in 21 patients was 89.7 points (72 to 100). We found a significant post-operative reduction in talar tilt and anterior drawer sign (chi-squared test, p < 0.001). The functional outcome of the procedure was excellent in ten patients (48%), good in seven (33%) and fair in four (19%). The results in terms of ankle function and stability did not deteriorate with time and there was little restriction in movement.

This procedure is simple and effective with a very low rate of complications.

Introduction

We performed humeral head replacement (HHR) with smaller head for closing the cuff defect in patients of cuff tear arthropathy (CTA). And also, if the cuff defect could not close by decreasing the head size, we add muscle tendon transfer such as latissimus dorsi transfer for posterosuperior defect and pectoralis major transfer for anterosuperior defect.

Introduction

In recently, Reverse shoulder arthroplasty (RSA) in patients with irreparable rotator cuff tear has been worldwidely performed. Many studies on RSA reported a good improvement in flexion of the sholulder, however, no improvement in external rotation (ER)and internal rotation motion (IR). Additionally, RSA has some risks to perform especially in younger patients, because high rates of complications such as deltoid stretching and loosening, infection, neurologic injury, dislocation, acromial fracture, and breakage of the prosthesis after long-term use were reported. Favard et al noted a 72% survival with a Constant-Murley score of <30 at 10 years with a marked break occurring at 8 years. Boileau et al noted caution is required, as such patients are often younger, and informed consent must obviously cover the high complication rate in this group, as well as the unknown longer-term outcome. Its use should be limited to elderly patients, arguably those aged over 70 years, with poor function and severe pain related to cuff deficiency. We developed a novel strategy in 2001, in which we used the humeral head to close the cuff defect and move the center of rotation medially and distally to increase the lever arm of the deltoid muscle.

In the Leiden University Medical Center (LUMC), the non-augmented direct repair method as described by Duquennoy for treatment of chronic lateral ankle instability, is used since the early eighties. To our knowledge, this procedure has not been described in English literature before. We performed a retrospective study, to assess the long-term outcome of non-augmented anatomical direct repair procedures, as originally described by Duquennoy. The procedure reassures ankle stability by retightening and reinsertion of the original talofibular and calcaneofibular ligament, without dissecting the ligamental tissue. The purpose of this study is to determine the long-term effects of the procedure in terms of postoperative quality of life, joint function and development of osteoarthritis.

Twenty-three patients who were treated in our institution between 1985 and 2002 completed the Short Form-36 Health Survey (SF-36) for assessment of postoperative quality of life and the Olerud Molander Ankle Score (OMAS) for subjective symptom evaluation. Clinical reevaluation, including physical examination of the ankle and the completion of the Ankle Society ankle-hindfoot scale (AOFAS) questionnaire, was conducted for twenty-one patients after a mean follow-up of 13±7 (range 3–22.2 years) years. At final follow-up radiographs were taken to assess the development of osteoarthritis. The mean total postoperative SF-36 and OMAS scores were 79.6 (SD ±14.6) points and 81.7 points (N= 23 patients) respectively. The mean total postoperative AOFAS score was 89.7 points (N= 21 patients). We found a significant postoperative reduction in talar tilt and anterior drawer sign. According to the AOFAS, the long-term functional outcome of the procedure was excellent in 10 patients (48%), good in 7 patients (33%), fair in 4 patients (19%) and poor in none of the treated patients. The results in terms of ankle function and stability do not seem to deteriorate in time. The procedure is seldom causing restriction in range of motion, neither a higher chance of degenerative changes in the ankle joint on the long term. We conclude that the procedure as originally described by Duquennoy is simple and effective, with a very low complication rate and does not provoke restriction in range of motion of the ankle joint.

The accurate reconstruction of hip anatomy and biomechanics is thought to be important in achieveing good clinical outcomes following total hip arthroplasty (THA). To this end some newer hip designs have introduced further modularity into the design of the femoral component such that neck­shaft angle and anteversion, which can be adjusted intra-operatively. The clinical effect of this increased modularity is unknown. We have investigated the changes in these anatomical parameters following conventional THA with a prosthesis of predetermined neck–shaft angle and assessed the effect of changes in the hip anatomy on clinical outcomes.

In total, 44 patients (mean age 65.3 years (standard deviation (sd) 7); 17 male/27 female; mean body mass index 26.9 (kg/m²) (sd 3.1)) underwent a pre- and post-operative three-dimensional CT scanning of the hip. The pre- and post-operative neck–shaft angle, offset, hip centre of rotation, femoral anteversion, and stem alignment were measured. Additionally, a functional assessment and pain score were evaluated before surgery and at one year post-operatively and related to the post-operative anatomical changes.

The mean pre-operative neck–shaft angle was significantly increased by 2.8° from 128° (sd 6.2; 119° to 147°) to 131° (sd 2.1; 127° to 136°) (p = 0.009). The mean pre-operative anteversion was 24.9° (sd 8; 7.9 to 39.1) and reduced to 7.4° (sd 7.3; -11.6° to 25.9°) post-operatively (p < 0.001). The post-operative changes had no influence on function and pain. Using a standard uncemented femoral component, high pre- and post-operative variability of femoral anteversion and neck–shaft angles was found with a significant decrease of the post-operative anteversion and slight increase of the neck–shaft angles, but without any impact on clinical outcome.

Cite this article: Bone Joint J 2015;97-B:1615–22.

Abstract. Reverse shoulder arthroplasty (RSA) is being increasingly used for complex, displaced fractures of the proximal humerus. The main goal of the current study was to evaluate the functional and radiographic results after primary RSA of three or four-part fractures of the proximal humerus in elderly patients. Between 2012 and 2020, 70 consecutive patients with a recent three- or four-part fracture of the proximal humerus were treated with an RSA. There were 41 women and 29 men, with a mean age of 76 years. The dominant arm was involved in 42 patients (60%). All surgeries were carried out within 21 days. Displaced three-part fracture sustained in 16 patients, 24 had fracture dislocation and 30 sustained a four-part fracture of the proximal humerus. Patients were followed up for a mean of 26 months. The mean postoperative OSS at the end of the follow-up period was 32.4. The mean DASH score was 44.3. Tuberosity non-union occurred in 18 patients (12.6%), malunion in 7 patients (4.9%), heterotopic ossification in 4 patients (2.8%) and scapular notching in one patient. Anatomical reconstruction was achieved in 25 patients (17.5%), the influence of greater tuberosity healing on shoulder function could not be demonstrated. Heterotopic ossification seems to affect OSS and QDASH, we found statistically significant relation between HO and clinical outcomes. Patients with heterotopic ossification had significantly lower postoperative scores on DASH and OSS (P = .0527). Despite expecting good functional outcome with low complication rate after RSA, the functional outcome was irrespective of healing of the tuberosities

Introduction. Revision total hip arthroplasty is often associated with acetabular bone defects. In most cases, assessment of such defects is still qualitative and biased by subjective interpretations. Three-dimensional imaging techniques and novel anatomical reconstructions using statistical shape models (SSM) allow a more impartial and quantitative assessment of acetabular bone defects [1]. The objectives of this study are to define five clinically relevant parameters and to assess 50 acetabular bone defects in a quantitative way. Methods. Anonymized CT-data of 50 hemi-pelvises with acetabular bone defects were included in the study. The assessment was based on solid models of the defect pelvis (i.e. pelvis with bone defect) and its anatomical reconstruction (i.e. native pelvis without bone defect) (Fig.1A). Five clinically relevant parameters were defined: (1) Bone loss, defined by subtracting defect pelvis from native pelvis. (2) Bone formation, defined by subtracting native pelvis from defect pelvis. Bone formation represents bone structures, which were not present in the native pelvis (e.g. caused by remodeling processes around a migrated implant). (3) Ovality, defined by the length to width ratio of an ellipse fitted in the defect acetabulum. A ratio of 1.0 would represent a circular acetabulum. (4) Lateral center-edge angle (LCE angle), defined by the angle between the most lateral edge of the cranial roof and the body Z-axis, and (5) implant migration, defined by the distance between center of rotation (CoR) of the existing implant and CoR of native pelvis (Fig. 1B). Results. All data are presented as single values as well as median and [25. th. , 75. th. ]- percentile (Fig.2). Bone loss was 53.6 [41.5, 76.7] ml with a minimum of 19.0 ml and maximum of 103.9 ml. Bone formation was 15.7 [10.5, 21.2] ml with a minimum of 3.5 ml and a maximum of 41.6 ml. Ovality was 1.3 [1.1, 1.4] with a minimum of 1.0 and a maximum of 2.0. LCE angle was 30.4° [21.5°, 40.1°] with a minimum of 11.6° and a maximum of 63.0°. Implant migration was 25.3 [15.1, 32.6] mm with a minimum of 5.4 mm and a maximum of 53.5 mm. Discussion. Within this study, 50 hemi-pelvises with acetabular bone defects were successfully quantified using five clinically relevant parameters. Application of this method provides impartial and quantitative data of acetabular bone defects, which could be beneficial in clinical practice for pre-operative planning or comparison of surgical outcomes. Including a larger number of cases, this method could even serve as a basis for a novel classification system for acetabular bone defects. For any figures or tables, please contact the authors directly

Aims. Various surgical techniques have been described for total hip arthroplasty (THA) in patients with Crowe type III dislocated hips, who have a large acetabular bone defect. The aim of this study was to evaluate the long-term clinical results of patients in whom anatomical reconstruction of the acetabulum was performed using a cemented acetabular component and autologous bone graft from the femoral neck. Methods. A total of 22 patients with Crowe type III dislocated hips underwent 28 THAs using bone graft from the femoral neck between 1979 and 2000. A Charnley cemented acetabular component was placed at the level of the true acetabulum after preparation with bone grafting. All patients were female with a mean age at the time of surgery of 54 years (35 to 68). A total of 18 patients (21 THAs) were followed for a mean of 27.2 years (20 to 33) after the operation. Results. Radiographs immediately after surgery showed a mean vertical distance from the centre of the hip to the teardrop line of 21.5 mm (SD 3.3; 14.5 to 30.7) and a mean cover of the acetabular component by bone graft of 46% (SD 6%; 32% to 60%). All bone grafts united without collapse, and only three acetabular components loosened. The rate of survival of the acetabular component with mechanical loosening or revision as the endpoint was 86.4% at 25 years after surgery. Conclusion. The technique of using autologous bone graft from the femoral neck and placing a cemented acetabular component in the true acetabulum can provide good long-term outcomes in patients with Crowe type III dislocated hips. Cite this article: Bone Joint J 2021;103-B(2):299–304

Abstract. Introduction. MCL injuries often occur concurrently with ACL rupture – most noncontact ACL injuries occur in valgus and external rotation (ER) - and conservative MCL treatment leads to increased rate of ACL reconstruction failure. There has been little work developing effective MCL reconstructions. Methods. Cadaveric work measured MCL attachments by digitisation and radiographically, relating them to anatomical landmarks. The isometry of the superficial and deep MCL (sMCL and dMCL) and posterior oblique ligament (POL) was measured using fine sutures led to displacement transducers. Contributions to stability (restraint) were measured in a robotic testing system. Two MCL reconstructions were designed and tested: 3-strand reconstruction (sMCL+dMCL+POL), and 2-strand method (sMCL+dMCL) addressing anteromedial rotatory instability (AMRI). The resulting stability was measured in a kinematics test rig, and compared to the ‘anatomic’ sMCL+POL reconstruction of LaPrade. Results. The sMCL was isometric, centred on the medial epicondyle, and the primary restraint of valgus. The dMCL elongated rapidly in ER, and was the primary restraint of ER near knee extension. The POL slackened rapidly with flexion and only stabilised the knee near extension. With sMCL+dMCL+POL deficiency (‘grade 3’), the 2-strand AM reconstruction restored all stability measures to native, apart from internal rotation. The 3-strand reconstruction restored all stability measures to native. The LaPrade reconstruction did not control ER, lacking a dMCL graft, or valgus in flexion, being anisometric. Conclusions. This work has revealed the importance of the dMCL in stabilising AMRI as part of anatomical MCL reconstruction, with the sMCL restraining valgus

Introduction. An understanding of anatomic variability can help guide the surgeon on intervention strategies. Well-functioning thumb metacarpophalangeal joints (MCPJ) are essential for carrying out typical daily activities. However, current options for arthroplasty are limited. This is further hindered by the lack of a precise understanding of the geometric variation present in the population. In this paper, we offer new insight into the major modes of geometric variation in the thumb MCP using Statistical Shape Modelling. Methods. Ten participants free from hand or wrist disease or injury were recruited for CT imaging (Ethics Ref:14/LO/1059). 1. Participants were sex matched with mean age 31yrs (range 27–37yrs). Metacarpal (MC1) and proximal phalanx (PP1) bone surfaces were identified in the CT volumes using a greyscale threshold, and meshed. The ten MC1 and ten PP1 segmented bones were aligned by estimating their principal axes using Principal Component Analysis (PCA), and registration was performed to enable statistical comparison of the position of each mesh vertex. PCA was then used again, to reduce the dimensionality of the data by identifying the main ‘modes’ of independent size and shape variation (principal components, PCs) present in the population. Once the PCs were identified, the variation described by each PC was explored by inspecting the shape change at two standard deviations either side of the mean bone shape. Results. For the ten MC1s, over 80% of the variation was described by the first two PCs (Table 1). Figure 1 shows the effect of the variation in PC1. The majority of geometric variation of the ten PP1s was also described by the first two PCs, with PC1 describing 78.9%. Figure 2 shows the effect of this component on the mean bone geometry. Both the distal articulating surface (head) of the MC1 and the proximal articulating surface (base) of the PP1 vary in overall size. However, the MC1 head also varies in shape (curvature), whereas the PP1 base does not appear to undergo noticeable variation in shape. In this study population, smaller MC1 was observed to correlate with a flatter head, whereas the PP1 head shape did not vary with size. Discussion. The flatter MC1 head (smaller height-radius ratio) may have implications for MCPJ instability, and possibly for osteoarthritic degeneration. A recent study predicted similar trends for the first CMC joint. 2. Previous investigation also observed correlation between MC1 head curvature and MCPJ RoM. 3. , which may explain clinical observations of differing thumb movement strategies. This study used a convenience sample and cannot describe a full population's variability, though the high variance captured by only two PCs suggests adequate external validity amongst similar populations. Further confidence would be gained from studying the joint (i.e. single PCA containing both bones), and wider populations. Significance. These data: provide more precise description of anatomic variation; may offer insights into thumb movement strategies and MCPJ osteoarthritic degeneration. 4. ; and support implant design for individuals whose anatomy can bear an anatomic reconstruction. For any figures or tables, please contact the authors directly