Analysis Of Biomechanics And Clinical Efficacy Of Rotational Scarf Osteotomy In The Treatment Of Hallux Valgus

Hallux valgus(HV)is a very common foot deformity.More than 200 surgical procedures have been documented in the literature,of which Scarf osteotomy is one of the most commonly used surgical procedures.It is mostly used for symptomatic moderate to severe hallux valgus,the intermetatarsal angle(IMA)is 14°～20°,the distal metatarsal articular angle(DMAA)is normal or slightly increased,the bone mass sufficient patients.However,the "troughing" of the Scarf osteotomy after translation and the limitation of the width of the metatarsal diaphysis,which affect the corrective ability of this operation,make its indications limited and many postoperative complications.In recent years,rotational Scarf osteotomy has been gradually applied,which can effectively avoid the "troughing" and improve postoperative complications in the treatment of hallux valgus.However,there is no previous literature report on the specific difference between the rotational Scarf osteotomy and the traditional translational Scarf osteotomy in terms of correction ability,biomechanics,etc.,and which method is more advantageous,and further research is still needed.Finite Element(FE)analysis has been widely used in medicine,especially in the field of orthopedics.By simulating specific body structures(such as bones),including the corresponding soft tissues for specific mechanical analysis,complex and detailed exploration has been favored by many researchers.The literature shows that the finite element method is used to analyze various mechanical characteristics of hallux valgus,and different types of operations can be simulated to explore the advantages and disadvantages of each other.Not only is the display clear and accurate,but it can also be used as a powerful supplement to the biomechanics of cadavers,and can effectively guide the choice of surgery in clinical practice.Studies have shown that rotational Scarf osteotomy can correct hallux valgus angle(HVA)and IMA while increasing DMAA,affecting postoperative function of patients with hallux valgus and increasing the risk of recurrence.Therefore,the rotational Scarf osteotomy is mainly suitable for moderate to severe hallux valgus patients with small DMAA and incongruency of the metatarsophalangeal(MTP)joint.The literature reported that the data on the evaluation of the congruency of the MTP joint in hallux valgus vary widely,Patients with the same degree of hallux valgus have large differences in the degree of matching of the metatarsophalangeal joints,and there are also large differences in the choice of surgical methods.The previous literature on measuring the congruency of the MTP joint is only to observe the degree of parallelism of the articular surface by the naked eye,lack of quantitative measurement indicators,and cannot be used as an indicator for evaluating the efficacy of pre-and post-operative hallux valgus surgery.Therefore,it is necessary to find an index that can effectively measure the congruency of MTP joint,which can not only quantitatively measure the matching relationship before surgery,but also help the selection of surgical methods,and can also evaluate the postoperative efficacy.Objective:1.To evaluate the correction ability and biomechanical difference between rotational Scarf osteotomy and translational Scarf osteotomy on hallux valgus by means of finite element analysis;2.To evaluate and optimize imaging indicators affecting the congruency relationship of the first MTP in patients with hallux valgus.In addition,it provides a basis for guiding the selection of surgical methods for hallux valgus and quantitative evaluation of the congruency relationship of the MTP;3.To evaluate the clinical efficacy of rotational Scarf osteotomy in the treatment of moderate to severe hallux valgus patients with incongruency of metatarsophalangeal.Method:1.The CT data of a patient with hallux valgus was selected to establish a finite element model of hallux valgus.Based on the model,the standard Scarf osteotomy was simulated,and rotation and translation were performed respectively.The sizes of different indicators such as IMA,contact area,DMAA and absolute length of the first metatarsal bone were recorded after every 1° rotation and every 1mm translation of the distal metatarsal block.On the basis of the bone model,the cartilage,ligament and other tissues were perfected to establish a full foot model.After the boundary and loading conditions were perfected,the troughing,the tension of the plantar aponeurosis,the plantar soft tissue,and the ground were analyzed.The stability of the fractured end was observed by equal parts stress and three-point bending experiments.2.Patients who underwent weight-bearing X-rays in the outpatient system were selected,and factors such as trauma,deformity,and surgery were excluded.Finally,183 patients with hallux valgus and 245 feet were included.Indicators such as HVA,DMAA,metatarsophalangeal joint angle(MTPJA),congruency index(CI),tibial sesamoid position(TSP)were measured.The differences of different imaging indicators in patients with mild,moderate and severe hallux valgus were analyzed between congruency and incongruency of the MTP.The sensitivity,specificity and critical value of two new measurement indexes,MTPJA and CI,were calculated.3.A total of 245 patients with hallux valgus who were treated in our department from September 2010 to January 2019 were collected,and 36 patients(38 feet)with moderate to severe hallux valgus and metatarsophalangeal joint mismatch who underwent rotational Scarf osteotomy were selected.The HVA,IMA,DMAA,MTPJA,CI,first metatarsal length,functional score,and complications were evaluated before surgery,6 weeks after surgery,and at the last follow-up.Result:1.In terms of the ability to correct IMA,rotational osteotomy has a greater ability to correct IMA.When correcting the same angle of IMA,the contact area of the rotating group is larger.In terms of the length of the first metatarsal,with the increase of the correction angle,the difference in the absolute length of the first metatarsal caused by the two methods first increased and then decreased.However,in the measurement of DMAA,the rotating Scarf shows a significant disadvantage,which can significantly increase t he DMAA.After loading,in the translational model,the cancellous bone and cortical bone contact site showed greater stress in the cancellous bone.It shows that the contralateral cortical bone will squeeze the cancellous bone,which is the cause of the troughing.In addition,the stress distribution of plantar fascia,plantar soft tissue and ground showed no significant difference between the two groups.The three-point bending test shows that the broken end separation of the rotational Scarf is also slightly smaller than that of the translational Scarf,and the separation increases gradually with the increase of the loading load.2.The higher the degree of hallux valgus was,the higher the proportion of incongruency of the first MTP joint.Significant differences were found in the DMAA,MTPJA and CI between the congruency and incongruency groups of patients with moderate-to-severe hallux valgus(P<0.05).The areas under the curve(AUCs)of the receiver operating characteristic(ROC)curve for DMAA was 0.554(P>0.05).However,the MTPJA and CI were 0.906 and 0.884,the sensitivity values reached 0.791 and 0.949,the specificity values were 0.862 and 0.644,and the critical values were 10.67 and 0.765,respectively.The correlation test indicated that in the congruency group,the DMAA and HVA were positively correlated,but the MTPJA,CI and HVA had low correlation coefficients.The DMAA and HVA were not correlated in the incongruency group;however,the MTPJA and HVA were significantly positively correlated,and the CI and HVA showed a negative correlation(P<0.05).3.The HVA at 6 weeks after operation and at the last follow-up were significantly lower than those before operation.In addition,compared with 6 weeks after operation,HVA showed an increasing trend at the last follow-up,and the difference was statistically significant(P<0.05).The two postoperative IMAs were significantly improved compared with those before surgery,and there was no significant difference between the last follow-up and 6 weeks after surgery(P>0.05).There was no significant change in DMAA and the length of the first metatarsal between preoperative and postoperative time points(P>0.05).The CI and MTPJA at 6 weeks after operation and at last follow-up were significantly better than those before operation,and there was no significant change at last follow-up compared with 6 weeks after operation(P>0.05).In terms of functional score,all three score results showed that the last follow-up was significantly improved compared with that before operation,and the difference was statistically significant(P<0.05).In terms of complications: 2 patients with hallux valgus recurrence in the 38 feet,3 patients with metatarsalgia,1 patient with toe numbness,and 1 patient with stiffness of the first MTP.Conclusion:1.Compared with the traditional translational Scarf osteotomy,the rotational Scarf osteotomy can correct a larger IMA,extend the length of the first metatarsal within a certain range,significantly increase the contact area of the broken end,effectively avoid the "troughing",and the separation of the broken end is small,which is helpful for postoperative stability and healing.Rotational Scarf osteotomy also has disadvantages,which can increase DMAA accordingly.For patients with larger DMAA,other surgical methods should be considered clinically.2.The MTPJA and CI are indicators that can be used to quantitatively evaluate the congruency of the first MTP joint,taking 10° and 0.765 as the demarcation points,respectively.Congruency of the MTP joint should be considered when choosing surgical methods for different degrees of hallux valgus,and the MTPJA and CI can be used as quantitative evaluation indicators.3.Rotational Scarf osteotomy in the treatment of moderate to severe hallux valgus with incongruency of the MTP joint can significantly improve the deformity of patients and improve the congruency of the MTP joints,with a significant effect.